I've noticed that when you travel in other states and you order corn on the cob, it's different. Here we call it sugar corn. It's bicolor and so delicious! I've been places where the corn is all white.
The most common corn on the cob here comes from a variety of sweet corn. I'm not sure about the specific variety though. I think it differs from establishment to establishment.
Here in upstate New York, we either have feed corn, for animal feed, or sweet corn for human consumption. There are tons of varieties of both. Sweet corn can be yellow, white or bi-colored.
We have sweet corn here too (as well as field corn for animals). I went to Georgia once and went to a local fruit stand and the corn was white. It wasn't sweet either, it was horrible!
The corn I grow here in CA, is green chopped for dairy feed. All dairy feed corn, that I seen, the kernels are yellow and being green chopped around 110 days, about 15 days before full maturity, that's when it has the best feed quality for cows.
Yes, field corn is everywhere. Most edible corn I see is grown on a patch of someone's backyard. I have no idea what kind it is, but corn on the cob has always been my favorite side dish