I’m not sure what you are getting at. If you’re really just interested in getting the color of a given set of pixels to equal another, then use the Match Color function from the Adjustments menu. For proper color correction, use all other tools and persistent color samplers (Alt+Eyedropper tool to place them, info palette to show their values). Understand, that exactly matching a color technically must not necessarily provide a good-looking image, so the obvious solution is not the most advisable one.
Mylenium
Here’s an example.
I photograph a piece of painted wood straight on.
I then photograph it at a 45% angle.
I want the color of the wood to match, but not lose any texture or detail. I can use my color sampler to read the RGB values of the straight on shot. How can I use those values to tweak the RGB numbers in the angled shot? If I add a color overlay of those numbers, its a solid fill and I lose the detail below. Lowering the opacity of the overlay lets too much "under color" show through. Is there a way to read the RGB values and adjust them "on the fly"?
"…If I add a color overlay of those numbers, its a solid fill and I lose the detail below…"
To preserve the overlay color but the underlying luminous detail, put the overlay in "Color" blend mode
