[Q] Password changed, gmail on android keeps syncronizing!

Hi. I have a serious issue. For working needs a colleague is given the password for a gmail account and he setted this account on his android phone. Now I want to stop the possibility for him to accede and so I've changed the password via web. But I noticed on my android that gmail keeps syncronizing every mail, despite I've changed th pw! Obviously also my collegue is able to receive all emails yet!
I hope someone of yours can help me!
Sorry for my english