By controlling current flow into RGB LED using potentiometers, a combination of colours can be realised on a pseudo analog scale (based on potentiometer swiper resolution but close enough).
Protect resistors of 50ohms are included to protect LED from destruction. When Potentiometers are at 50ohms, transistors conduct about 26mA (enough to fully turn on LEDs).
Power supply voltage was chosen based on forward voltage of each LED colour (GB had higher forward voltages than R; hence, a higher power supply voltage to get same current was required).
Play around with potentiometers to get different colours… enjoy :)
