goshdogit
(goshdogit)
3422
Nice mod, dk21291! 
I found several listings for RGB cycling 5mm LEDs on Amazon.
Here’s one to get started.
The listing specifies 3 to 3.2 Vf. This page says the Yuji 5mm LEDs from the first run C01 are 2.7 to 3.1 Vf. A quick search indicates the Sophia 5mm LEDs from later models are 3 Vf.
Seems like these RGB emitters would do fine in both versions.