I never really had a close look at the Histogram paintjob before mine, and whilst I originally thought it was just a staggered fade or something similar between colours, turns out Garret Chow's 'design' is actually a really shitty cityscape that a kid might draw as the background of his schoolbook sketch of Batman.
This is a histogram, in the context of photo editing software:
This is a histogram, in the context of photo editing software:
Which is why it looks like / is called that.