Stupid ass washing machine...
Why do people seem to think that every sector of a military must have it's own uniform? Standard BDU's are commonplace in today's world, let alone 500 years from now. Besides, I personally think that the uniform we're seeing on the CEA marines/Reach army troopers is really cool looking and certainly an improvement over previous BDU's.
As for their gear, nobody really knows. But I'd imagine that due to the technological advancement from now to then, a super-light, super-tough metal/plastic/fabric has been discovered or developed. MJOLNIR armour is most certainly impervious to ballistic rounds.