Why does Illustrator keep changing my color?

You'd think these were two different colors right? But no, the hex keys are the same for both. I'm not sure why Illustrator is doing this...it's recent so it seems like an update I missed and don't know how to fix.
Whenever I try to change the color, it'll choose a slight complementary color, like below. There's no transparencies set on the stroke and really only appears when I start adding colors to the object.

Does anyone know what this is and how to fix/remove this feature?
