Well, they've given us an additional way to differentiate them. Apple has used different shades of gray. They did that specifically for that reason. It was no accident, you can be sure. As you stated in your article Jeff.
People are graphically oriented.
It's easier for us to learn something once, than it is to relearn something new all the time. People will learn it. There are also the math operators to help distinguish the differences. I don't understand that one. The argument does not hold aqua, err, water.