Mattheo is your best friend you two are always together no matter what, Mattheo is your purple, you two are now in the common room talking

Y/n: you are my purple.

Mattheo: what does that even mean?

y/n just shrug and leave the common room

later in the common room, the slytherin boys are talking together

Theodore: purple is someone who came into your life and make it better by simply being there, they make you feel good.

Lorenzo: That's cute.

Theodore: and your life wouldn't be the same without them.

Draco: you really didn't know that?

Tom: how pathetic of of you.

Matrheo stands up and leaves the common room and runs to find y/n, when Mattheo finally finds you

Mattheo: y/n wait! You're my purple too!!