I've always wondered this. I know that unlike membrane keyboards, mechanical keyboards interior isn't like 50% air, but is it all that hard to put the same multiple color LEDs as there are available on some membrane keyboards?
I mean, I know that Costar has already showed a prototype keyboard with dual colors:
And that there are custom keyboards with custom LEDs such as the Max Keyboard, but that's not selective.
But why is it that dual-color keyboards only arrived now and why was it so hard to make a keyboard with that?