Green is the wrong color. They also have to be logged in to the live chess server to accept challenges. So let me run down the article...
https://support.chess.com/customer/portal/articles/1444882
Live is the second part.
Inviting Friends to Live Games
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Hi, I'm trying to invite some online friends to live games. I can clearly know they are online because I see the small green square in their profile image. But whenever I go to add them, the app says "username" is not currently available for live games. We checked, and his account is accepting challenges from anyone.
Why is it being difficult? Please help! Thanks in advance.
~Nic