I've been doing photography, as a hobby and sometimes, as a profession, for 50 years. I started using Photoshop when I bought my first digital camera about 20 years ago. I'm going to post some samples of my work along with youtube videos that explain some of the techniques I've used, for anyone that is interested.
This is a pic posted by a famous sports personality. I'll let you guess who. The one on the left is the original. The one in the middle is an intermediate step where I stripped out all the color and improved the overall density and contrast. In the one on the right, I added color, as I imagined it might have looked.
This video is a decent tutorial on how to colorize a black and white photo. There are hundreds more, with more advanced techniques. Gotta love youtube.