The PSI in the films always cross faded from blue to red.
Most of the time the display was blue and red at the same time.
A lot of R2D2 models use a single Bi/Tri colour LED for the PSI so this effect isn't possible.
I decided to use 4 Tri colour LEDs which I can control via a strip board of my own design connected to an arduino. The arduino controls the position of the fade, for this demo it sweeps it from one side to the other and then back again. An arduino may seem like overkill for a simple led controller, but this arduino will also control all the hardware in the dome.