Think a sharpie might look kinda sloppy, but how about some car windo tint? Most shops that carry it have it from very light all the way to limo tint, and it should be pretty easy to mount to a clear acrylic. Haven't seen it done yet, but it would'nt cost very much to try it out I'm thinking.
Before installation of tubing, shows cutting of fan grills, and MB Tray paintjob:
Watercooling C/W, also painted up and mounted some refrigerator casters to bottom to help make the case more mobile.
Pic of front with 2 x XSPC dual bay res/pump combo's. I got rid of the door for now, may...