>>392533394
use alpha mask and do an alpha gradient?

Right click on a layer and click "add alpha mask", then you have two pictures per layer - one is the actual picture, another is black and white transparency map, which you can edit if you click on it. Use gradient tool to make it smoothly fade out. Then you color will desaturate smoothly, and you can have multiple color layers overlapping and blending like that.
In theory.