Do you think a possible reason why Adrien and Mari can't identify each other behind the mask is because they view the world differently when suited up? Like how Mari only sees the world in black and white so she really can't see what Chat Noir's hair color/eye color is?

Eh, if you really want my answer, the canon reason is just Clark Kenting. Astruc has also confirmed that their vision is totally normal, and the “bug vision” is more like a visually-shown thought process than what Ladybug literally sees.