Not sure what you mean by 'severe colors'. I didn't know that there was a problem with LEDs having 'severe colors'.
All a matter of Artistic Interpretation. He (?) doesn't like the colors provided by the original product, and wants to experiment with additional options...
The industry hasn't seemed to address this yet.
I'm not sure I'd say that. If you go to an actual LED manufacturer, you'll find LEDs in a much wider variety than the usual selection from low-cost hobbyist providers. "Amber", "red-orange", "teal", "Traffic-light green", etc. I suppose that most RGB LEDs are designed with chip wavelengths optimized for "mixing" in industry-standardish ways, but perhaps the current "RGBW" smart LED chips would come closer to what you're looking for - in addition to RGB, they have a white section (your choice of cool, natural, or warm) as well... They're not THAT much more expensive, on a per-LED basis. And "smart." Bulkier, though... Adafruit NeoPixel Digital RGBW LED Strip - White PCB 30 LED/m : ID 2832 : $69.75 : Adafruit Industries, Unique & fun DIY electronics and kits
(It looks like you can get RGBW dumb strips as well...Analog RGBW LED Strip - RGB plus Cool White - 60 LED/m [~6000K] : ID 2440 : $79.80 : Adafruit Industries, Unique & fun DIY electronics and kits)