Choose RGB or CMYK for book printing from the current specification for the exact production route. KDP currently recommends CMYK for paperback cover images. IngramSpark currently requires CMYK for its cover and color-interior images. Lulu currently recommends sRGB for its print PDFs and converts other color spaces to sRGB. A black-and-white route may require grayscale. Keep the editable source, use the provider’s export settings, inspect the resulting PDF, and use a printed copy for decisions about physical color.
Should a book file be RGB or CMYK?
There is no single answer that fits every book printer. The correct color space is the one required by the current production route for that specific file.
The platform differences are real. KDP’s current paperback-cover page recommends CMYK images. IngramSpark’s current File Creation Guide requires CMYK for cover images, and its checklist requires CMYK for color-interior images. Lulu’s current guidance recommends sRGB for its print PDFs and says other submitted color spaces are converted to sRGB.
That means converting every file to CMYK because “print equals CMYK” can be wrong for a workflow that expects sRGB. Sending sRGB because it looks vivid on screen can be wrong for a workflow that requires CMYK.
Ask one question before converting: What color space and profile does the production provider currently require for this interior and cover?
Interior and cover may have different instructions
Do not assume a cover requirement automatically applies to the interior. A provider may publish separate guidance for color interiors, black-and-white interiors, covers, jackets, or a particular product line.
Record the requirement beside the file name. For example, keep a note for the interior export and a separate note for the cover export. That prevents a correct source file from being converted through the wrong preset at the last step.
What do RGB, CMYK, and grayscale mean in a book workflow?
RGB
RGB represents color using red, green, and blue components. Screens, cameras, and many digital illustration workflows use an RGB space. A label such as sRGB or Adobe RGB adds a defined interpretation of those component values.
RGB alone is not a complete output instruction. Two RGB spaces can describe different ranges and appearances. If a provider asks for sRGB, do not send an untagged RGB file and assume it means the same thing.
CMYK
CMYK represents color with cyan, magenta, yellow, and black components used in many print workflows. Adobe notes that CMYK working spaces are device-dependent because they describe actual ink and paper conditions.
For that reason, “convert to CMYK” is incomplete advice. A conversion needs a destination condition or profile. Choosing an unrelated generic profile can change saturation, dark detail, neutrals, and total ink in ways that do not match the selected printer.
Grayscale
Grayscale uses tonal values without color channels. Providers may require grayscale images for a black-and-white interior. This is different from leaving a color image inside a file and expecting the print workflow to make every conversion perfectly.
IngramSpark’s current checklist calls for grayscale images in black-and-white interiors. Lulu’s current PDF guidance likewise tells users to set black-and-white images to grayscale.
Current KDP, Lulu, and IngramSpark color rules differ
| Provider and file | Current direction | Important boundary |
|---|---|---|
| KDP paperback cover | CMYK recommended for cover images | KDP removes profiles and warns against mixed spaces and unsupported spot colors |
| Lulu print PDF | sRGB recommended | Other spaces are converted to sRGB in Lulu’s workflow |
| IngramSpark color cover and interior images | CMYK required | RGB and spot colors can be converted and produce unexpected results |
| Black-and-white routes | Often grayscale | Follow the chosen provider’s specific interior instructions |
Amazon KDP cover guidance
KDP currently recommends CMYK for paperback cover images. Its cover page says color profiles are removed before publishing and warns that profiles can produce unexpected results. It also advises against mixing color spaces in one file.
KDP’s print-on-demand route does not support spot colors. Its current guidance recommends converting spot colors to CMYK. These facts belong to the KDP cover workflow and should not be copied into an unrelated printer’s instructions.
Lulu print-PDF guidance
Lulu currently recommends exporting color print PDFs in sRGB. It says other color spaces, including CMYK, are converted to sRGB and that this conversion may create unexpected print changes.
Lulu also notes that converting CMYK to RGB does not eliminate color variation. The correct response is to prepare for Lulu’s workflow, inspect the result, and keep physical-color expectations realistic.
IngramSpark guidance
IngramSpark’s current File Creation Guide requires CMYK for cover images. Its current PDF checklist requires CMYK images for a color interior and grayscale images for a black-and-white interior.
The guide warns that received RGB and spot colors are converted to CMYK before printing and that the conversion can produce unexpected results. It also contains workflow-specific limits for ink density, black construction, and profiles. Use the current guide rather than extracting one CMYK label from it.
Use a provider-first color workflow
- Keep the editable master. Preserve original RGB artwork, layers, text, and linked images before any production conversion.
- Name the exact destination. Record provider, product, interior type, cover type, paper, and any supplied profile or preset.
- Separate interior and cover decisions. Confirm each file’s current requirement.
- Work on a production copy. Do not overwrite the only color master.
- Convert with the required settings. Use the destination profile, PDF preset, or export path supplied for the job.
- Inspect difficult colors. Check saturated blues, greens, oranges, dark shadows, skin tones, neutrals, and small colored type.
- Export the PDF and inspect it. Do not approve from the source application alone.
- Review the digital proof. Look for obvious conversion, transparency, or object errors.
- Use a printed copy for physical color. Screen approval cannot prove the paper-and-ink result.
Do not repeatedly convert an image back and forth between RGB and CMYK. Each conversion maps colors into another space and can discard or alter information. Return to the preserved master when a new destination is required.
Handle spot colors and black separately
A spot color is not automatically supported by a print-on-demand route. KDP and IngramSpark both instruct users to convert unsupported spot colors for their current workflows. Ask the provider how a special ink, metallic color, varnish, or brand swatch is handled before building the file around it.
Black text and rich black backgrounds can also have different construction rules. Do not use a four-channel rich black recipe for small body text unless the provider directs it. Follow the current values and ink-density limits for the selected route.
How do you check color spaces in the exported PDF?
Acrobat Pro’s Output Preview can inspect separations, color spaces, output conditions, ink coverage, and object information. Its Object Inspector can show the color mode and other properties of the content under the pointer.
Use the current production profile or simulation condition when the provider supplies one. A generic simulation cannot reproduce a press, paper, and ink combination it was never built to describe.
Check for:
- objects remaining in an unintended RGB, CMYK, grayscale, or spot space;
- unwanted profile assignments or missing profiles where the workflow expects them;
- black text converted into multiple process channels;
- unexpected color changes in transparencies and imported PDF objects;
- dark areas with lost detail after conversion;
- different color handling between the interior and cover.
Preflight can find technical conditions, but it cannot decide whether an illustrator prefers one mapped blue over another. Technical inspection and visual approval answer different questions.
Why does printed color look different from the screen?
A monitor emits light. A printed page reflects light through ink or toner and paper. The available colors, contrast, black point, brightness, and surface response differ.
Adobe explains that soft-proof reliability depends on the monitor, monitor profile, destination profile, output device information, and ambient light. A calibrated display and a suitable simulation profile can improve the preview. They cannot turn the monitor into the finished object.
Paper changes the result too. A bright coated sheet and a warm uncoated sheet do not present the same white point, saturation, or shadow detail. Production variation can remain even when the file is correct. KDP notes that environmental and mechanical factors contribute to color variance in its POD model.
Use the digital proof to catch preparation mistakes. Use a physical copy to judge the physical color, paper interaction, surface, and real viewing conditions.
Book PDF color-space checklist
- Confirm the exact provider and product.
- Read the current interior and cover color instructions separately.
- Preserve the editable color master.
- Record the required RGB, sRGB, CMYK, or grayscale destination.
- Use the supplied profile, preset, or written conversion path.
- Convert unsupported spot colors as directed.
- Check black text and ink-density requirements.
- Inspect the final PDF with the appropriate production tools.
- Review the complete digital proof.
- Reserve exact physical-color judgment for a printed copy.
Color space is one part of a production file. Image resolution, page geometry, bleed, margins, fonts, page order, and cover construction still need review. Use the wider print-ready PDF checklist and the current File Guide.
Frequently asked questions
Should I convert every book image to CMYK?
No. Convert according to the actual provider’s current instructions. IngramSpark currently requires CMYK for its color images, while Lulu currently recommends sRGB for its print PDFs.
Can I send an RGB cover to KDP?
KDP’s current paperback-cover guidance recommends CMYK images and warns against mixed color spaces. Follow the current KDP instructions for the exact product before export.
Why does Lulu recommend sRGB for printing?
Lulu’s current workflow uses sRGB and converts other submitted spaces to sRGB. This is a Lulu-specific production instruction, not a universal print rule.
Does a CMYK file guarantee accurate printed color?
No. The destination profile, paper, ink, printing process, conversion settings, proof, and production variation still affect the result.
Can a digital proof show exact printed color?
No. It can reveal preparation and placement problems, but the screen cannot reproduce the complete paper-and-ink result.
Can YourBookBound check my color file?
The current workflow begins with a free human file check before payment. Send the complete interior and cover so the team can review the actual files and tell you whether they fit the supported service scope.
Color prepared, route still uncertain
Send the complete book file.
Start with a free human initial check. No payment is required at upload, and there is no obligation to order.
Official references
- Amazon KDP: Create a Paperback Cover
- Lulu: Interior Formatting, The Basics
- Lulu: PDF Creation Settings
- Lulu: Color Differences
- IngramSpark: File Creation Guide
- IngramSpark: PDF File Checklist
- Adobe Acrobat Pro: Color Management and Composite Printing
- Adobe Acrobat Pro: Color-Managing Documents
- Adobe Acrobat Pro: Color Conversion and Ink Management
- Adobe Acrobat Pro: Preview PDF Output