I'm learning digital painting in Photoshop, beginner level. I start with a composition in grey-scale, Let's say it is a mountain landscape in perspective with darkest object closest to viewer (a tree on a cliff) and lighter grey the further off into the horizon objects are (mountains).
Now I want to start applying color but preserve the values from the grey-scale sketch. I have a black & white adjustment layer on top of my drawing that I toggle to check that the values remain the same as I start applying color. Let's say I want the foreground to be green and red. How do I find greens and reds with the same value (amount of black) as in my grey scale concept drawing? Currently I just test out colors by handpicking them from a swatch palette and viewing them through the b/w adjustment layer, but there must be a more systematic way (I hope) to generate swatches from a value. Any advice or pointers in the right direction are highly appreciated.
(I'm using Photoshop CS4).