3mm RGB LED is sort of RGB LED (Tri-color LED).
It is mainly aimed at the LED keyboard lamp market because it have small in size and is also with the spotlight of the through-hole LED.
3mm RGB LED have three chips in, four pins, common cathode or common anode and those chips can be placed arbitrarily.
For the 3mm RGB LED, the lens can be water clear or diffused. The former has a strong spotlight, and the later lens will make people feels soft.