This concept, known as Interpose in M&M is something of a favorite of mine. Over on my blog I wrote about this in the context of MHR. Colossus isn't the only one who's doing it, so you could swap out the two other official SFX that handle it.
Also, there's nothing in Colossus' SFX description that implies you can't simply spend a second pp to ignore the stress through Invulnerable. Just saying.
Interpose: That’s Mutants & Masterminds speak for intentionally getting in the way of an attack meant for another character. It’s a damned heroic thing to do, but it’s not explicitly mentioned in the Marvel Heroic book that I can find. There are a few SFX that come close so I’ll call them out here. On Colossus’s datafile there’s this one:
SFX: Take the Hit. Spend 1 PP to take physical stress intended for a nearby ally or friend.
This one is clearly meant to represent Colossus standing between an attack and it’s intended victim. Very heroic. There’s also Invisible Woman’s datafile with this one:
SFX: Reactive Power. Spend 1 PP to add a Force Projection power to another character’s dice pool before they roll a reaction. If that character takes physical stress, take d6 mental stress.
This one is more for using a power to protect another character rather than doing it bodily. Again, very heroic stuff.
The Civil War Event book gives us the character Goliath and this version of interpose:
SFX: Human Shield. When a nearby ally or friend takes physical stress, you may step up that stress to take it yourself instead.
So far this is hands-down my favorite iteration of this concept in MHR. There is no cost to the play other than the stress inflicted. This explicitly heroic behavior is further reinforced by tying this action into the character’s milestones, earning him XP for using this Human Shield SFX.