Okay, here me out.
I think Sam and Colby were dating before Sam met Kat.
When Sam met Kat, he and Colby broke up. When Colby realized how serious Sam and Kat were, he started to drift away from Sam because he still loves him. That's why we see Colby looking at Sam longingly sometimes.
Now, I think maybe something happened with Sam and Kat and Sam and Colby have gotten closer again.
Idk, just a theory. And maybe I'm alone in this but just some late night thoughts.
