This may seem like a simple question but its integral that i know this while building a Giant Killing Team and I just cant find it in the rules. Can a colossal size ( symbol just to clarify) make a ranged combat attack while adjacent to a normal sized figure?

Yes, just not against the said adjacent opposing figure, unless the Colossal has Pulse Wave.

Oh well that bites! Will rework my strategy. Thanks for the quick response! I'm gonna take me down a nemesis.

The rule is on the PAC:
Note that the size of the opposing characters doesn't matter.