How much more does a book with colored answers cost to print?

KDP prices a color interior by the whole page count, not only the answer pages, so every copy costs noticeably more to print than the same book in black and white, and you need a higher list price for the same royalty. Check your book's real cost with KDP's printing cost calculator before you choose. To keep the book in black and white, leave "Answers at the back" off and give the answers away as the answer key PDF.