Top flite has a poster with a bunch of color schemes: [link=http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXJA14&P=7]Trim Scheme Poster[/link]

I haven't used any of the schemes exactly, but it gives some good ideas. Also, I just do a quick outline of the plane on paper and use colored pencils to try out different ideas - quick and cheap.