These signs are typically installed as multiple circuits due to having a lot of lights (even the led ones are usually split, and the split tends to be vertical or diagonal). The installers have some discretion as to which letters/words go on which circuit, so it’s possible the installers did this semi-intentionally, but really it’s just a byproduct of how large signs are lit.

In this case the other letters are probably the same color, the circuit just broke for whatever reason.