The RGB LEDs under the joystick are not in separate compartments, when one is lit with a specific colour it unfortunately bleeds into the other LED colours. You need to have some separators between each LED to make a nicer effect. I cut some pieces of card and the plastic diffuser to divide each LED under the joystick into a separate compartment so that the colours do not blend together. Perhaps something like this could already be done in a future version of the joystick.

EDIT: I've noticed that when using the joystick it is difficult to hold it to see all 4 LEDs at the same time, one LED is usually obscured by your thumb in the direction you are pushing the stick . I've now changed back my modification because at least the blended colours give a small indication of which direction is active. I still think the ring of separate and not diffused LEDs on the JoyC is a much better effect.