It was bugging me today that the color bars were a bit muted - not as vibrant as I would expect; it became really obvious when the colors transition - it almost appears to drop to black.

After a bunch of testing and re-examining the board I realized that I used some 750ohm resistors instead of 75ohm - so it dropped the voltage level much below what I expected... I know I tested the voltage levels before... but.. somewhere along the lines of my intense 2 week debugging and refactoring I must have made a mistake. 

So now the colors are as vibrant as I'd expect!

The only issue is some minor noise where the colors change... I haven't been able to track this down yet but I'm sure it's related to capacitors or resistors - I'll keep an eye out for it as I wait for my DAC for full 4bit color :)