There isn't really a set standard but approximation 6500K tends to be the default setting. The temperature will drift with aging/wear aswell, since monitors basically never had cathode calibration like all the better TVs did, which constantly monitor beam current on every color against a reference and hold thing there until the tube is too worn for electronics to compensate. Monitor will simply get worse and worse and will require manual adjustment every now and then to keep things in an optimal state.

With the monitors that lack user adjustments for color, there are potentiometers inside the monitor, usually on the neckboard. You can restore color balance and gain from there, or at least make things less bad, depending on how much wear there is.

The old blurry VGA screens like my Tandy VGM with the old slot grid were definitely set warm from the factory. Ditto on the 15khz Magnavox Amiga screens

As the years went on things went more “blue” in the color balance (cool)

Very late crt screens had it selectable

Mid 90s IBM P70 17" trinitron with digital controls had 3 selectable color temps IIRC

Thanks for the information all. The Compaq I have certainly seems blue-ish, so I'm wondering if it's colour drift more than intention - my undertanding was that 9300k was typically more a Japanese setting, though even then the discussion seems to be around consumer sets rather than PC monitors.

I've set the Compaq aside for now at least. I have a trust Packard Bell monitor to fiddle with.

When you do a grey scale using grey scale bars (8 to 9 bars of grey or color bars still work) with color knob all the way down, it is neutral color temp. Slight adjustment of red and green slightly warms the temp while still in the grey scale. Wrong set blue settings, kills the warmth. So I get neutral greyscale first then, warm it slightly. When color knob is reset to just right you might see some warmth.

When I was in TV repair shop, I adjust all RGB with tone midway, contrast midway, brightness midway, and color off with customer settings reset to defaults, with video input of grey scale test image. The key is white is not blown out (too up keyed aka too much brightness and any of rgb brightness also,) and perfect black in black bar. I end up with prefect picture quality. Not too hot nor look wrong. Note I use internal red, blue and green adjustment or service menu to obtain the neutral grey scale.

Aged CRT will get you nowhere as when you get it right, the color trails off like over-bright comet tails or for example, the red get too bright and loses detail. Also raster lines comes up too is another sign. Game over.

Cheers,