Just stumbled across a neat LED that shows rainbowcolors by itself: http://www.superbrightleds.com/moreinfo/component-leds/rgb-slow-color-changing-led/778/ Has only 2 pins and with a few of these you can make a real multicolor rainbow. Just switch them on separately with a four seconds delay.

2 pin RGB rainbow-LED

Topic		Replies	Views
Any one willing to help out a DIY noob? LEDs and Multiplexing	10	3187	May 6, 2021
"Rainbow" LEDs Interfacing	10	3140	May 6, 2021
Rainbow LED Deutsch	9	2046	May 6, 2021
Is that possible to use only 2 pins with rgb led ? LEDs and Multiplexing	5	4825	May 6, 2021
RGB Led Strip Exhibition	7	4704	May 6, 2021