I have a black and white portrait, and I would like to put a transparent pink colour overlay onto only the person's coat, that way you can still see the texture of the coat. Thanks!
You must be able to select the wanted pink area with available selection tools. Polygonal lasso, Quick selection tool, Pen+make selection etc... OR colour an oversized area and cut the exessive area off. If you still struggle with big accurate selections, use the cut-method.
Create a new layer, make it have blending mode =color or hard light
Paint pink to that new layer over the coat. Do nor worry about the borders paint a little too large area. Play with the layer opacity slider, try different pink versions and compare the modes hard light and color. The latter give more saturation. If needed, erase the painting and redo it with new color.
You might want to do some color tests without new painting. For that is adjustment Hue/Saturation. It makes possible to adjust already painted colors. When used as an adjustment layer it's even possible to readjust and point to a wanted area by adding a layer mask and still you will retain the full editability.
When you are happy with the effect, cut the exessive pink off by eraser and by drawing selections around areas to be removed by DEL. The easiest tool to this is the polygonal lasso tool.
Sometimes the image has good contrast border that can be used for selection. You can use for example the Quick selection tool in image layer and then continue in the new pink layer.
To be fast you must at first learn, how selections can be
- expanded by pressing shift and selecting more
- contracted by pressing Alt and selecting the exessive area that should not be selected
Here's an example. The Pink layer has blending mode = hard light and its opacity = 42% Sorry that I forgot to make it visible in the layers panel.