I think its really a new couple things. (Not related to seungmin couple) but I'm a big shipper of sungjoy redvelvet joy and yook sungjae. Before sungjae went to military service this two change color too. Joy like blue most of her insta post she's wearing blue and admit that she's into to blue lately. Then sungjae into to color green with us represent joy. That's why all of their shipper believes that they really dating Because of solid proof.
And now I believe of SEUNGMIN too. I think this is their way of showing to their supporters that their together. Like what heechul said that idol and celebrities proof that they are dating through their clothes and couple things.
I will stand my beliefs that SEUNGMIN is real.
Ps. Sorry for the long post.๐