If you'll get used to Illustrator it will save you some work down the road.... As long as you're cutting covering by hand, Photoshop or Paint will work fine. If you ever need to go to a CNC lettering or covering cutter, however, it will need vector based input. The EPS format that Illustrator (or Freehand, etc...) can output is much easier to convert to the CNC instructions....
Photoshop, Paint Shop Pro ("poor man's Photoshop"), or GIMP (free!) are sort of the standards for editing color schemes for models in G3.5...
-Case
ORIGINAL: ArmedZagi
You wont hear me laughing about Paint... I've done the covering schemes for 1/2 of my planes that way. Although I have to admit. it sure is nice to have photoshop now.