On the topic of Hazbin character designs being too red, I'd like to add that having red in most or even every character's design isn't even a problem. The Team Fortress 2 cast is designed the same way to make it clear that they're all on the red team
But no one criticizes the TF2 designs because Valve was still careful about the shades and placement. It's so subtle that it's not overwhelming but still apparent enough for you to be able to tell who is and isn't on your team. Even Spy's suit is almost entirely red, but it's still a desaturated red (almost brown) so it's easier on the eyes.