Help CenterOnce your project is completed and you are ready to download it, you have 2 choices.
Click on "Download" on the drop down menu in the Studio.
Your choices are "Download Current Project CMYK (Printed Books)" & "Download Current Project RGB (eBooks)".
In short, if you are doing a printed book, choose the CMYK version, and if it is for the screen, like an e-book then choose RGB.
See this detailed article in the Book Bolt Blog section of our site, “RGB” vs “CMYK” – The Comprehensive Guide To Book Color Formats.
You can choose RGB to upload to KDP, but in the end, it will print in CMYK with Amazon printers.
Keep in mind that RGB mode creates the maximum color combinations, with 16.7 million colors compared to CMYK's 16,000 possibilities. Despite having more color possibilities, RGB files are usually smaller than CMYK files. So something on a screen will always look much better than in print. Print is still pretty good though. So a Neon color on your screen may look great, but it just will not print the same at all.
One other thing, we should mention, is color printing is expenses, especially on premium paper. Please check the price if thinking of doing one, before spending a lot of time on a project and realize a 100 page premium color hardcover must sell for a minimum 22.77 to make 1 cent royalty off the book. KDP Printing Costs and Royalty Calculator.
Also there is this article that may help as well from UC San Diego, Color Models. It goes deeper into the whole CMYK and RGB world!
Here is another article about CMYK and Hex Codes that you may find helpful. Also, one more article explaning the difference between PMS, SMYK, RGB and Hex. Just to overload your brain more, one more article here as well on RGB vs. CMYK. Maybe one of these help you understand better than another.
For color charts on CMYK we offer a couple of links here, from All Colors Website and from Mixams Website.
For a CMYK Calculator W3 Schools Website offers one.
One last one, from Convert A Color Website which will convert colors for you between your preference.
Another article we have on CMYK is this on, Are There Websites That Will Tell Me the Hex Code or CMYK Code for a Certain Color?