Learn how to Color Tone images using the Gradient Map tool in Photoshop.

A Gradient Map is similar to a Levels Adjustment layer except that it applies different colors to various light levels. Gradient Maps are primarily used for coloring and toning images.

Dive into gradient maps with this one minute tutorial by Adobe Creative Cloud (How to Make a Duotone Effect in Photoshop CC) or go a little deeper with How to Color Tone Using Gradient Maps by PHLEARN.

In the example below the only edits made were a Gradient Map layer with a bit of the jackets and helmets masked to bring back some of the blue, and a few touchups on the wall using the healing brush.

Before and After