You can open the mixer window for the device being used to record and see the input levels .. plus RB does show an input level VU. So the suggestion to draw a line or trigger a color change on a clip is (often) already available in the input device software. I'd rather see the waveform drawn out as suggested.

It may require better optimization in other areas of the software to accommodate, but I like the idea.

I do not work here, but the benefits are still awesome
Make your sound your own!