Plum 96, Neo Zelia, Pure, Poker II would be my top suggestions depending on what you are looking for. They all support LED and have traces and a controller firmware that will work even on models that don't have any leds out of the box. Of course you can also always get some backlight model of a keyboard too and simply change the led colors in sections or whatever you have in mind. If you choose the leds wisely and stick with the same fV color groups it is pretty minimal effort involved. If you want to mix low fV colors like red, with high fV colors like blue it gets more tricky, but still manageable if you select super mad bright high fV leds that will look normal at a lower voltage. Yes all MX switch support LED, but not all PCBs do.