Are you saying you can't start a games or just that you can't select white or black?
If the game doesn't start it could be to do with your, or your chosen opponents challenge settings.
Otherwise it could be a fault.
If you like I'll send you a challenge to see if it works for me
I only play 7 :14 or longer though.
What colour shall I select for myself?
I just posted an open invite, and selected black for myself. It worked fine. The green 'play as -----' button only shows up on the games you are eligible to accept. So I cannot see anything on my game because I cannot accept it. However, it does show up on all games that I qualify for.
So when you put up an open invite, do you see the game listed at all? If it's there at all, then I think you're good to go. You will not see the accept button yourself because you cannot accept your own game, but others will see it if they meet your setting limits.
Do you see the game at all that you have set up? (other than the green box)?
You will never see the green box in an open invite game that you have created and posted.
That is because you cannot accept your own game.
The green box only shows the games of others that you are eligible to accept.