This is a trick that everyone knew back in the day but it's possible they don't anymore, since dvGarage is no longer much of a thing.

When you're putting together a composite and you need to color correct one layer to match another -- say matching a greenscreen foreground to a sunset background plate -- color correct each channel (R, G, B) separately while looking only at that channel. That way you're matching black, white, and grey points on greyscale images, and your eye is much better at distinguishing differences in luminance than chrominance. Get each channel to the point that it looks like the foreground and background belong together in greyscale, and nine times out of ten the full RGB image will be nailed.