It’s named the Color Mixer in Lightroom CC (the Cloud version), and simply the Color Panel in Lightroom Classic, and the video above (from Adobe’s own Michelle Wei & Josh Haftel), shows how to adjust individual colors using the panel.
NOTE: Their tutorial is using Lightroom CC (the cloud version), but the HSL / Color Panel works the same way in Lightroom Classic, but the interface looks slightly different (click directly on the word ‘Color’ in HSL / Color). Across of the top of CC’s panel are color swatches in circles; in Classic they’re rectangles. Click on one of those rectangles in Classic and you’ll see the same sliders appear that you see in the video.
Thanks Michelle and Josh.
Hope you have a better-than-average Tuesday!