TMBG and "the doctor said don't do that" humor

We went to a They Might Be Giants show today, and you loved it. It was pretty much the same as a grown-up TMBG show, right down to the puppet-to-human ratio on stage.

This evening, in the car:

You: If you see a blue light, say “aaaahhh! there’s a blue light!”

Me: [Seeing some blue in a nearby neon sign] Aaaahhh! there’s a blue light!

You: No, a round blue light.

Me: Oh, I don’t see one of those.

You: They’re on the red light and the green light. [Probably-accurate translation: there are traffic signals with blue lights about somewhere.]

Me: Ok, wait. If a red light means ‘stop’, and a yellow light means ‘the light is about to turn red’, and a green light means ‘go’, what does a blue light mean?

You: It means “look out! there’s a blue light!”