It’s always amusing to think of how much of our everyday lives, things we take for granted, are actually based on fallacies.
When you go into a bathroom and you look at the tap you will sometimes see the colours blue and red, indicating the temperature of the water depending on which tap you turn.
Of course, we don’t question this. We all know what it means. Red…think of a red hot coal on a barbecue, is hot. Blue…think of the lips of a freezing corpse in a chilly morgue, is cold. You get the image.
But the reality is that that when something is heated (and I mean really heated) it goes through several colour changes. Paradoxically, red is in fact the coldest of the colours when something is heated. The next temperature stage up from red is white and the hottest temperature colour is…you guessed it…blue.
Probably best to stick with H and C for the taps.
NASA (With appreciation and attribution to Earthsky.org)