Maybe it's just that I like the change of pace from the landscapes I've been going over for the past 10 years. Call me crazy.
I'm pretty certain that the streamer has no control over this phenomenon. What causes it I do not know, but for a few seconds at least in those games I get a taste of something different. A horse of a different color. + Show Spoiler +
A shiny pokémon, if you will.
EDIT: Pictures added!
Weird colors:
Cool colors: