An adjustment layer is an independent layer of color adjustment that you can edit any time you like. Plus, it affects all layers below it, consumes very little space in memory, and affords the opportunity for selective edits.
Photoshop Tutorial. Selectivel Colorize an Image Part 1.
Learn one very simple way, using the mask of the Black & White Gradient Map Adjustment layer to conceal or reveal parts of the image in color and other parts as a black and white version .