I'm rubbish at reading signs.
If you tell a guy you're into something and he says 'hmm, very intriguing '.
If you're talking about music and he says, 'the real question is, do you like X band?'
If you say yes he says 'phew, I don't think I could know you anymore if not ;) '
He says 'after we've had such a great discussion on X, I'm going to do X tonight'
He teases you about things, it's hard to give a written example as such but if you say you're doing one thing and he says 'Nahh come on, what are you doing that for? Do X instead ' in a playful sort of way.
I walked into the room once and he was talking to another colleague about me, in a positive way.
When I said I was transferring he said he hoped we'd still talk.
It's so hard to know, if he is just friendly or not or if it's mild flirting. He also goes a bit red sometimes.
It's a no go though, it's not worth getting involved with colleagues for me. I tried to test the waters by asking about previous dating experience and he said he hadn't wanted to date in his previous office for the same reason.
So I guess it will just be an office crush :(