Open the image, turn the artwork into grayscale, and then turn it into sRGB.
Create a new transparent layer, and then use the brush to color the place where you want to add the color, and then change the layer blending mode to a filter.
Fill a little gray and darken the whole hue.
Fine-tune the curve, brighten the whole
Finally adjust the optional color in the white, complete, it is so simple!
Final effect DiagramCategory: