I know what you mean! I didn't catch it until my (mumble, mumble, ahem) REPEATED viewings and once you see it, you can't unsee it. So I really don't know what was going on there. Did Rumlow honestly think he could take Cap down in his suit? (Arrogant arse probably thought so...) Or did he just figure it wouldn't matter much what Steve was wearing?

I have no idea. And I've never seen a deleted scene in between those two points to account for the costume change.

(And I don't think it was stealth paint on the shield LOL---Ellidfics, in one of her "Captain Fraudulent" series of stories, has Steve put a device on his shield that changes what the shield looks like. So I'm adopting as headcanon that the device she mentioned also gave the shield its stealth look. ;-))