I’m sure its been retconned somewhere down the line that predators can see in our vision mode too, and its suggested strongly in one of the movies… i think maybe predator 2. I don’t know how or why, but it makes little to no sense having predators with patterns and colours on their armor that they cannot even perceive when one subscribes to the whole “they can only see in IR”.
I think it was just a cool cinemegraphic choice in the original film, that didn’t make as much sense later.