When you design your cover, make sure you have it all just the way you want it color wise, pictures, text, everything. Then save it as a .JPG file and insert it as the first page of your book file. It will also have to be uploaded as the cover art. On Nook it will come out in color in both the sales ad and the first page of the book. On Kindle it will come out as color in the ad but will be in Black & White in the book. So make it easy on yourself when you creat your cover, save it as the right size and save both a color and a B&W image.