Please tell me their all the same color, not different for each button like some N64 or funky dance floor.
Someone posted a while ago that they changed the backlight to multiple LED's which they claimed increased the battery life of the thing quite drastically. It was obviously slightly darker, but that could be fixed, and the light wouldn't be as evenly distributed. But that sounds like a good mod if someone would like to write up an article on that. You could change the LED's for charging and charged and reminders pretty easily. Mine are about to fall out from when I opened my Casio to overclock

. If you found transparent buttons or made some yourself you could transfer those LED's to the buttons so that it looked funky. You could also hack out the IRDA port on the Casio's and put them in the front where they should be, where the old charge, charging, and reminder LED's would have been.