I created it as a minimalistic Christmas gift to friends and relatives, and I am quite pleased with the result - the transition is smooth, other colours can be implemented by changing the LEDs and the resistors, and only a small number of components is needed. Power consumption is also minimal, so there is no heat build-up, and it can be on all day.

The transistor count could be reduced, but they look like little ornaments on the tree so I left them as they were :) Soldering the Micro USB can be tricky (you have to bend the leads and elevate it a bit) but it's not a challenge for an experienced solderer.