I don't mind the colour actually, but I tihnk it could have been used a little better. Something needs to change in the backgorund and the hl2 logo could be toned down a somehow.
When I think of Opposing force, I think of green, white and black . Hence, the green fits . But I agree, maybe a bit too much. Its good, just needs some excitment around it, maybe Corporal Shepherd, some headcrabs or some screenshot. You also know that you have Half-Life 2 and then opposing force. So unless the extremely unlikely case that a mod called that does come out, you're a bit stuck .
The number of fonts used is a bit excessive seeing as its so simple. Three fonts for three(four) bits of text? You should've put "" around the "I want to believe..." as well, might've looked like a comment rather than a name. Text is a bit bland...