Electrical – Toggle between two colors in a common-cathode RGB LED using a SPST switch

I had this problem when I was making a propeller display. We bought some clear lens leds but we were getting this same problem. More precisely, the cause is that there are 3 physically different LEDs inside the package. Now there are two options which worked for me. (But take all of this advice with a grain of salt since I worked on simple 5mm low power LEDs, as the size and power goes up things change.)

1. Change the LEDs and get diffused lens ones. Like this here. I really don't know why someone would want a clear lens one. But I don't know much about optics. If you are really careful you can just use sandpaper to make the outer surface diffused, but I would not advise that, since I damaged some LEDs by doing that, before I got good results.

2. Another way is to use something to diffuse the light. I know you used lenses but those worked for me, and I don't know why they didn't work for you. Maybe a pic showing your setup would give us a clearer idea. I got good results with covering them with a little butter paper. Normal paper could be used, but of course that will dim the lights way too much.

It will probably be more aesthetically pleasing to transition between colors using the HSV colorspace.