Automating in-game process

Question

Hello, sometimes I play an online browser-based flash game. You can join either of the two teams that play against each other, and there is a "join" buttom for each team. The problem is, the games where my friends play are usually full and I have to wait until someone leaves, you have to press the join button as quick as possible, otherwise someone else might enter. What I'd like to do is to write a program that would analyze the state of the "Join" button (it becomes darker when there's a place available in a team), move mouse cursor to the button and press it for me.

I have enough programming experience in general, but I have never done anything like that before, can anyone give me any advice on where to start?