I posed this once before and got some good advice, but it involved creating transparent alpha channels in Photoshop, etc., and I keep wondering if that's going the long way around.

I have a wooded scene (a woman approaches from the distance, for opening credits for a short film) which is cut between two sequences with snow on the ground. I tried using the V4 color corrector to turn the lighter leaves on the ground white, to resemble patchy snow, but the effect makes the "white" leaves give off a vibrating "buzz" like crazy.

After this, I applied the "glow" FX effect, turned down slightly, and it created spots of white "snow" in place of the lighter leaves plus a nice white haze on the skyline (and unfortunately, on the raincoat worn by a passerby). I can live with this (and therefore recommend it as a hint for others), but I can't help but wonder if there's a way to "paint" larger patches of snow inside color selection(s). The camera was mounted on a unmoving tripod.

As a footnote, I shot the film with the Panasonic DVX100 at 24p, so I also wonder if the Monday update which allows editing in that camera's 24p mode, might eliminate the visual "buzzing" effect in a color selection. If nobody knows, I'll try it and post the result.