1. the name i think youre looking for is called "color selection"
2. I do it a slightly different way than you do it which is i make a selection of what i want to be in the original color (using whatever tool you want and refining the edge) and then copy that selection to a new layer. From there, you can do whatever you want with the background layer (saturation, hue, temperature, ect.)
let me know if you need any further help!