That's interesting, I never looked. Now I feel like I should go drive off 100 miles to check if mine does the same...
Yes, that's what it does--if you drive it too far it will turn red. You should also see a power limit bar.
True that! Yellow and green make brown. Drive it a bit farther and it turns more yellow. It does not, however, turn from yellow to orange to red. It goes from yellow directly to red. That's when you know you really MUST stop. Experience is a GREAT teacher, but she can be harsh!
Interesting, I hadn't seen the multiple shades of green->yellow. To me it was always a two color change.