specular is just the colour it reflects so if you do your cheat line green it'll reflect green, do it red it reflects red, the only map thats colour dependant and a really big load of work is the bump map... specular is an easy one, for the fuselage colour unless its metal i use a very slightly lighter colour, and for metal i actually use a load of greys and my own ENVmap... but as i said spec map is in full colour just like the main bits you'd normally paint.