So please explain (in 20 words or less!) the other numbers in that screen and why your magenta change didn't totally mess up the skin tone.
Well, this takes a bit of investigation and judgement. At the top right, is a tiny eye dropper. Click that guy onto the reddish extensions and it will embolden the LETTER of the color that is most heavily part of that hair.
In this case, the M was in bold. Sometimes, when a blue sky is too light or too dark, you may have to tweak CYAN along with blue.
The rest of the boxes are RGB showing applied red, Yellow, Green, Cyan, Blue , Magneta, as applied to the red channel. .. and so on. Maybe I can find the video, but just play by typing in numbers that amplify.
Fred
Found a decent video of Sel Colorhttps://we.tl/t-vilaci3Hjg