Ancient beast that I am, and my less-than-rich (monetarily) youth, meant that I grew up in what might reasonably be called the final days of the common vacuum tube. The CRT lasted longer, and the magnetron lives on in microwave ovens (and RADARs, yes), and I expect that higher power transmitters will be using tubes for some time. And X-rays will remain tube-generated for the foreseeable future.
That meant that switching something on was not instant gratification, but a bit of a delay as the filaments warmed up and then they warmed up the cathodes, and only when the cathodes were hot was the gear truly in the operating state. And the filaments stayed on and glowing orange. This is hardly of any note nowadays with transistors and integrated circuits doing all the old work and then some in almost every case. But it can be a bit jarring when there is some internal LED (on the motherboard or some expansion card) that can be seen through ventilation slots. Blue, green, yellow/amber, and red are no big deal, for those are LED’s and obviously so. But one I pass by from time to time is a bit jarring. It’s orange. It’s if not that orange, it’s close enough in my memory that I sometimes have this moment of “Huh? Oh, right.”