Hi,

I got this purple ring promo Colossal Boy and I was wondering if defend would allow him to share his DV w/ all friendly figures up to two sqares away from him since he is a giant character?

Unfortunately no.

From the General HeroClix Errata and Clarifications:

When a character has powers or abilities that require adjacency to work (such as with Poison, Defend, etc), the giant character must be in an adjacent square (i.e. right next to) to the other character in order for either character to use those powers.