Originally Posted by AustinJerry
The blue filter method is a relic from the CRT days, so that folks without colour testing gear could try and approximate what the correct colour was supposed to be. But if you have calibration gear then it's completely unnecessary, because you've got a totally objective means of setting the colour, as opposed to the subjective (it's relying on your eyes' sensitivity to colour) blue filter method. If you're setting colour by eye, you're throwing your calibration out of the window
The blue-only mode is extremely accurate, and does not rely on your eyes' color sensitivity; it couldn't, because the image is monochromatic. The test relies on your eyes' sensitivity to small brightness differences, which works great. If the blue filter works for your display (i.e. it cuts out the red and green and you don't have wide-gamut display with an active CMS), then it's also quite accurate; more than accurate enough to be used by professionals. It's also fast and has very few gotchas. It's definitely the go-to way to adjust color and tint for displays that it works for. Using instruments is much slower.
With a colorimeter, you have the problem that some of them are really inaccurate with light sources with spiky spectra, and that sadly describes a lot of modern display technologies. So it's very possible to get a worse calibration with a colorimeter, if it can't read your display accurately.
Spectroradiometers (and good colorimeters) can read a display fine, but there is still some math to do to duplicate the blue-filter approach.
For Color, you read XYZ (in linear, non-normalized values) for white, red, green and blue (using windows, if possible, rather than just aiming at the patches on a color bar pattern). You adjust Color until Yblue = Ywhite - (Ygreen + Yred). Every time you adjust Color, you have to re-measure all four windows. When everything is right, the same equations should match for X and Z. If they don't come at least close, there's something wrong, probably a CMS or your colorimeter can't measure your display accurately.
For Tint, you measure red, green, cyan, and magenta, and adjust Tint until (Ycyan - Ygreen) = (Ymagenta - Yred). Again, every time you adjust the Tint control you have to re-measure all four colors. And again, once Y matches that should also be true for X and Z. If they aren't close, something is wrong.