Well, the consensus, as I suspected, is that they are to show (prove?) that the fluid levels have been checked.
If you ask me that's a dumb system unless you only plan to check something once. I guess you'd have to use different color paint each time. And why not mark the oil dipstick, the coolant cap, hell, the tire valve stems... then I could have a polkadotted technicolor hummer.
Thank you everyone who crawled under their hummer to look. Now I can pass my passive suggestive control psychology exam
Just kidding. I really was curious.