I thought I submitted something but apparently it got lost (I started seeing some of those website errors again earlier).
Anyway, like the other thread mentioned above, it's probably the evolution of new and different parts/suppliers for things like the LED that make the difference.
I did a comparsion of a PSR-800 side-by-side with a TRX-1 and while many colors are the same, some are slightly different. Yellow on the PSR-800 is a good yellow but it is slightly whiter/brighter on the TRX-1 with a slight greenish tint.
The nice thing is you have all the flexibility in the world with the colors on these radios....essentially more than a million color combinations (all of which of course won't look completely different - i.e. ff0000 and ff0001 probably look the same).