If I have a fairly solid color fading into another solid color, how can I change the second color and have transition area fade to the new color?
Is this a single layer?
Yes, straight off the digicam.
duplicate and desaturate the layer, play with the contrast until color A is white and color B is black, then copy the grayscale layer into the original layer's mask. you should now have color A fading into transparency (may have to invert the mask.) then place a layer filled with your desired color below
What exactly do you mean by mask? I'm new at this.
I did what I wanted to accomplish, and learned a lot about masks! Thanks for the help everyone!