Complex sentence: The OhmRGB maintained the Ohm64's controls, but introduced red, green, and blue LEDs behind each button, each addressable by MIDI messages such that a button could be illuminated with one of seven colors.
Split into simpler sentences: The OhmRGB maintained the same layout of the Ohm64's controls, but introduced red, green, and blue LEDs behind each button. Each LED is addressable by MIDI messages, such that a button could be illuminated with one of seven colors.