I spent enough time in aviation to know how much drilling it actually takes to teach people emergency procedures. If it’s different than what they usually do, it takes hours of practice. Even something as simple as finding and pulling a different door latch. If you’re stressed, even as stressed as “the doors won’t open the way I’m used to them otherwise everything is okay” your brain will just fail to pivot to the alternate procedures.
Cars got so simple to use in the 90’s. Sure they were simpler machines in the 60’s but fuel injection eliminated chokes and other carburetor issues, automatic transmissions became ubiquitous, children can handle vehicles of this complexity. And now we’re making them more complicated for no actual reason, with electric door latches with manual backups and such, and it’s causing problems.
To expand on this, the rainbow of colors which start at a straw then turn yellow, red, brown and then that vivid blue, are caused by refraction. The oxide layer on the surface is transparent or translucent, and the thickness of the layer determines what wavelength of light it scatters. The hotter it gets, the thicker the oxide layer forms, so you can fairly reliably tell the temperature the metal has been heated to by eye, and you might use different amounts of heating to achieve hard-but-brittle or soft-but-tough.
I’ve even seen it done by Chris of Youtube channel Clickspring for decorative purposes. It’s how he made the steel hardware of his brass clock blue.
Exactly how you temper something the size of a sword using a forge is a bit outside my understanding; I’ve done it with relatively small bits of drill rod to make lathe tools with a gas torch, but that’s about it.