RGB, CMYK and spot colours: fixing colour errors for KDP and IngramSpark's 'Color space used

Colour in a print file comes down to a few terms:

• RGB (red, green, blue) is how screens make colour, with light. Phone photos and web images are RGB.
• CMYK (cyan, magenta, yellow, black) is how printers make colour, with four inks.
• Greyscale is shades of grey only, which is what a black-and-white interior should be.
• A spot colour is a specific pre-mixed ink, often a Pantone colour, used in traditional printing. Print-on-demand presses print with the four CMYK inks, so spot colours get converted.
• A colour profile is a hidden note attached to a file about how its colours should look.

What the platforms say (as at 4 October 2026)

KDP recommends CMYK images on print covers. It asks you to leave colour profiles out (it removes them before publishing anyway), to convert spot colours to CMYK, and not to mix different colour types in one file.

IngramSpark checks for "Spot colors used" and "Color space used" when you upload. Its guide says cover images must be CMYK, and that RGB files are converted to CMYK before printing, which can shift colours. Black-and-white interiors should be greyscale with no spot colours or profiles; images in colour interiors should be CMYK.

Lulu is the exception: its printers work in both sRGB (a standard kind of RGB) and CMYK, and prefer sRGB. It still asks for greyscale in black-and-white interiors, and shows a warning for a unique spot colour.

Bookvault asks for a CMYK workflow where possible. Barnes & Noble Press doesn't publish an RGB or CMYK rule.

Why the right file looks duller

A screen glows; ink on paper only reflects light. Some bright RGB colours, especially vivid blues, greens and neon pinks, can't be made from four inks, so converting to CMYK pulls them back. A CMYK file on screen is a fairer preview of the printed book. The RGB version may look brighter, but it gets converted before printing anyway. Don't brighten a CMYK cover back up to match your screen: order a proof copy and judge the real thing.

How to fix it in Word

Word can't make a CMYK PDF. Its black text usually comes out as plain black, which is fine, but pictures keep whatever colour type they had (usually RGB). Here's what you can do in Word:

1. For a black-and-white interior, convert photos and drawings to greyscale in a photo program before you put them in the book. Word's own Recolour option changes how a picture looks, but converting the file itself is safer.
2. Set your text colour to Automatic or Black, not dark grey or a colour, unless you mean it.
3. Logos are the usual source of spot colours. Ask whoever made the logo for a CMYK or greyscale version, and swap it in (right-click > Change Picture).
4. If IngramSpark still flags colour space, the finished PDF needs converting to PDF/X-1a, a print version of PDF that only holds CMYK and grey. A program such as Adobe Acrobat Pro can do this, or a book formatter can.

Using a designer, InDesign, Affinity or Canva? Set the document to CMYK (greyscale for a black-and-white interior), convert spot swatches to CMYK, and export as PDF/X-1a:2001. For Lulu, sRGB is fine. If your design tool offers a CMYK option when you download a print PDF, use it for KDP and IngramSpark.

Check before you upload

Bervet's free spine width calculator checks interior and cover PDFs for RGB and CMYK images, spot colours and PDF/X, against each printer's rules. The check runs in your browser and nothing is uploaded; checking a PDF needs a free Bervet account. For ebook covers the rule flips (Kindle needs RGB): see Kindle ebook cover rejected.