I just realized that we have a way of talking about color - in Control Panel, click Display, then click Appearance, then where it shows color in desktop, click the color chip and it will let you click Other, and you can make a custom color by clicking on the spectrum.
I also just realized that I have already customized my desktop, and Microsoft blue isn't what I am using. It's Hue 160, Sat 240, Lum 75, Red 0, Green 0, Blue 160. Which reminds me of the color of cobalt blue when light is coming through it. And is almost exactly the same color as the new Atlantic Blue mustang. So we haven't been talking about the same color at all. Sorry.
The only solution is for us both (or all) to get a Munsell color chart (you'd expect the person who systematized color nomenclature to be German, right?):
munsell.com |