From my "Modeling the October Scene" clinic that I presented at the Cocoa Beach RPM meet and again at the NMRA National in Portland, Ore.
Some of the color combinations I use to flock the fall trees. They are arranged by basic color group (green, red, etc…)
Left side shows the basic material I use. Then the color that's added as a "highlight" color. To the right you can see the result when combined.
Note I do NOT "dunk" the tree armatures in the flocking material. I apply adhesive (usually thinned matte medium, though I've used hairspray in a pinch) and hold the tree upright and sprinkle the material from the top down. I don't try for 100% coverage - I try to let some of the fine branch tips remain bare to create the appearance of a tree that has changed color and shed some, but not all, of its leaves.