You apply "Adjustments > Brightness/Contrast". Default starts at 0 for both when you first open the image. Just increase it to the right till you get +50 Brightness / +100 Contrast. My original images have a very faded blue. The tweaked images have a much sharper blue than what appears in the game, but the scripts is able to actually read and match them, which is all that matters. Also, I set the images' tolerance in the script to 120.
It works for my screen/video card; try it for yours, and if that does not work then tweak the values until you find something that works for you.