Is it a major problem to color over a hand tinted photograph? Say for example, you found this photograph, and you really wanted to colorize it using your own color palette:
Would it be a crime attempting to remove the original color?
No. First, make sure it all the legal stuff has you in the clear (if the subject is a famous name, I would recommend leaving it alone), and then in Photoshop go to layer > new adjustment layer > black and white (for a helpful tip, on the layer, press auto)
From there, you should be good to go! Sometimes the the colors used will wash out the image when you use the black and white layer. Carefully tweak the levels and if that doesn’t work, very carefully try Levels/Curves layer.
If you have a problem with your color levels cooperating – after turning it black and white, flatten the image and then drop it into an entirely new file and see if that works. Or you could just do that anyway, lol. There are times Photoshop wants to read the old colors and won’t adjust to the new color you ask for. Making it black and white gives the program no choice.
Hope this helps!