It depends on how the book will be printed. On some books you'll have to use only black and white colors, on some others, you'll be able to use shades of grey. Make sure what options are allowed with your client, his publisher will know that
Hey there Max! Loved your Jardhen map, as always your city maps are fantastic!
I have one production question if you don`t mind! If I ever get a B&W comission, for a book let`s say, can I use shades of grey? Or it can only have Black and White as colors?
Thanks and sorry to bother you!