D.T.
Definitely a battle you shouldn't fight when they're too young. And just an FYI, I put an orange polo with camo shorts on both of my boys - they go great together! :o)
Have you tried putting 2 or 3 outfits out for them? That way you both win. You choose & they choose!
My 6 year old used to walk out of the house looking like Punky Brewster (I personally loved it), but now she knows when things "don't match" or don't go well together. Hey, in the big scheme of LIFE, this is one thing that doesn't matter so much. Being kind, loving, gentle, selfless, etc. are the things that really matter! So let them have a little fun (and control)!