When you are typing on the ebay sell your item form at the top of that box there is an A with a red box on it..highlight your item and click on the A and then click on the color that you want to use. The font size is to the left of that so you would do it the same way. Keep in mind that some colors are very difficult to read.
Many people don't read the whole listing so make sure that your shipping prices are in the proper shipping area. The prices in that area are what you charge regardless of what you have stated in the listing description area.