Todomomo

Navy Blue looks good on both of them. White does too. Black does. Momo might wear a Navy blue dress and he might wear a black suit with a navy blue dress shirt.

Kirimina

They both look good in black, white, and depending on the shade, purple.

Miruhawks

Pink or yellow. Dove wears pink a lot. Kind of matches her eyes.

Iidamei

Both look nice in lemon yellow, orange, and white but it's a hassle to get Mei to put in a dress so she wears rompers.

Kamijirou

Both rock black and white.

Dabi x Toga

Don't go to formal events but if they did, black and a bit of red.

Nejitama

Light purple and pinks

Mt.Kamui

Purple

Ryushot

They're wedding color, navy blue and sometimes they wear light purple together.

HitoRei

Black, blue, and whites

Tetsukendou

Turquoise and black.

SetSero

Green and orange