Colloquy + Google Talk = Possible?
I'm afraid it's not going to work. Colloquy is a client for the IRC protocol (also SILC and ICB, both of which are rarely used). Google Talk uses XMPP (aka Jabber) for its text chat, which Colloquy doesn't support.

If you want a 3rd party client for Google Talk, anything that supports XMPP/Jabber will do, but keep in mind this works only for the text chat. The VoIP capabilities require the Google client or website. iChat includes a Google Talk account option, you just need to fill in your Google ID and password:



Another popular Mac option is Adium, a multi-protocol IM client, that will do Google Talk as well as AIM, MSN, Yahoo and others.