@Numana Thanks
I did not change the lightning, only the color of wall/floor.
You can find the textures in the directories and edit them yourself :
...\pack\pack_dungeon\scenes\textures\floor
edit the file "concrete3_jpg.dds"
...\pack\pack_dungeon\scenes\textures\wall
edit the file "concrete2_jpg.dds"
If u want to modify all your dungeons you'll have to replace each file in each dungeon texture directory.
If u don't have Photoshop you can find free softwares that manage .dds files, i use paint.net (
http://www.getpaint.net/index.html) it's very easy for newbies

Take care to save the original file just in case you want it back.