Why did the tween colors change in 2019 and how can I Change them back to the original Color?

Hi WillieRiske

is that such a biggie?? I can't even remember how they were before 2019.

I think the classic tween hasn't actually changed. Get used to it

The Animate team changed the tween colors to better match the standard colors across Adobe desktop apps using the newest UI framework shared between Animate, Photoshop, Premiere, et cetera.

There is . currently no way to customize them but you can ask for this feature:  Feature Request/Bug Report Form