With the handicap of "no flying" for Tony I think that Colossus would beat him in an H2H confrontation. An enraged She-Hulk hit him and half of his systems went off line.
But if Tony can keep a distance which I doubt he can do(suit's ground mobility and manuverability) against Colossus who is enhanced in speed while in armoured form he can probably win. His armour has sonics and if Cyclops optic blasts can effectively further th gap against Colossus I'm sure Iron Man's repulsors, pulse bolts, uni-beam, and anti-tank missiles can do something.