Having same objects attach together?

Hi guys,

Let's say I have 3 different coloured balls. When the player shoots a particular colour I want them to pop/disappear if three of the same object touch each other. As they do in most of these games where different coloured balls go along a line and you have to shoot your colour to connect at least three of the same.

I assume the creation of them would be easy enough. Just have x number of different coloured balls, and spawn a random one each time the player shoots...

Thanks!