Red gauges would make more sense for heat.

[bonyetty]

What the hell are these little green bars that keep popping up. I'm guessing this is what most people thought when the green progression bars for heat popped onto the screen. I'm sure there is a reason the dev chose green to represent overheating. Mmmm I'm puzzled. Coders why wouldn't the Dev responsible choose RED for this purpose?

[TMS]

They turn red just before your RAM explodes.

[bonyetty]

Doh lol

[Temeter]

They also get a red outline and start glowing red when they get hot. There is even an 'overheat' marker for engines (not for tanks/equipment, tho), so most players should understand the system quite fast. Depending on how long the RAM survives.

[Wallygator]

I suggest they choose black and white to address accessibility for colour blind users(or at last provide the option)

[problemecium]

I was slightly puzzled myself when they first showed up, oblivious to what they meant. At first I guessed they were "HP bars" and I started to get concerned when I saw them going down even if I throttled down the engines. Fortunately I checked the changelog shortly thereafter xD

[AlphaAsh]

They turn red just before your RAM explodes.

This. The new heating mechanic is very simple. If your stuff gets too hot, KSP crashes in despair. It's not a bug. It's a feature.

[Sky_walker]

I was slightly puzzled myself when they first showed up, oblivious to what they meant. At first I guessed they were "HP bars" and I started to get concerned when I saw them going down even if I throttled down the engines. Fortunately I checked the changelog shortly thereafter xD

That's really a bad sign.

It should be obvious without looking into documentation / change log. I don't know, perhaps they should make it look like a thermometer (and make it vertical) instead of making it horizontal bar that by default appears green?

I fully understand your confusion. The fact that a first time you see it is pretty much always an ascend phase of the flight doesn't really help.

[michaelsteele3]

I think I figured out what it was when I first saw it, since I was messing around with the re-entry heat with HyperEdit. (Don't try that a home, kids)

[mattinoz]

I thought they were green so they stood out over all the red flames but if they turn red before the bang my assumption is wrong.