I've been a member of dojos that did the colored belt thing and dojos that didn't. I understand awarding colored belts in kids classes but overall I tend to go with the KISS principle when possible and would prefer the white-until-black.
I kinda like that my dojo does white, brown and black. I think the brown belt at least gives you a better idea how far along a kyu ranked person is. Helps me know how to adjust my intensity.
Not into rainbow colors and I certainly don't think that coping an attitude on someone at a seminar, who gives advice is wise. You never know just who you are training with. For instance suppose some yundasha forgot his belt and is wearing a white on loan for a day?
I hope I don't develop such an arrogant attitude as I progress. I'm all for the, nod and smile and either try out their suggestion or just keep doing what I'm doing until sensei comes to correct whichever of us is wrong.