The solid colored background, is exactly that..... whatever works, and is the color that you'd like it to be. The trick to acheiving such results is to keep the background a couple feet behind your subject ( or atleast having your depth of field correct for the circumstances), or having the correct lighting to make it appear as it does in person. A solid color background is usually about the last thing you need to worry about, atleast until you've got your subject in focus and well represented.