What colour is sperm / semen?

Sorry for the question. Hubby and I had sex this morning and I normally keep a bit of tissue down there for a little bit to catch the semen. This morning it seemed to have the most tiniest bif of colour. I couldn't tell if it was pink or yellow, it was that faint. AF is supposed to start tomorrow and I'm wondering if it's possibly some of that (I do normally spot in the leading days) or if it's possibly a bit of a yeast infection (as I have felt a little bit uncomfortable down there these last few days). Sorry for the TMI. We are TTC so it would be great if it were the latter.