There are many mice with multicolor LEDs on the market right now, any reason why there is no such keyboard yet? Are those LEDs more expensive than normal ones or need some additional technology implemented?
because first there is the size issue. Only very small led can fit in the switchs, so any bigger leds will need to be put aside from the switch.
Then there is the energy problem. You need a lot of led to fully illuminate a keyboard. And USB has only a limited supply(expecially on a laptop). So you need very low voltage leds if you want to use a lot of them. Or your keyboard won't work because it needs too much energy supply on certain computer (a cheap usb hub, or a laptop, etc…)
Finally, you need a huge amount of I/O pins on your microcontroler to be able to control each led separately. This means a way more complicated PCB, and a more expensive microcontroller.
On a mouse, this is a lot easier, as you only have a few leds. Not ~100.
