Don't know if this would work or not, but couldn't you possibly just lighten the colors of the textures in whatever art program you use?
A great program i use is GIMP. [But you can use any program you'd like! :D]
STEPS:
1) Open up the textures in GIMP
2) Click on the texture [texturename.jpg]
3) Go to Colors and wait for the drop-down. "colors" should be between Layers and Tools
4) Click on Brightness-Contrast...
5) Make it how-ever bright you want by using the two scroll bars and moving them to the right
6) Save it! ;)