When we open the Materials palette and select a color, we see a series of values ​​that maybe we sound like 'Chinese' But between them, we will be able to 'read' two that can help us when Colorize an image:

Are indicated by arrows and vary depending on the selected color. To check, just to seleccionéis observing them as different colors and change the values ​​that never go out of 255 I chose a blue color:

and enter the values ​​127 and 255.

We will now open an image that could be jpg or psp format. I use a jpg. And placed on it will go to Adjust / Hue and Saturation / Colorize: We will get a new window where we will insert the above values:

We can from these values ​​play with the tones, and to guide us with specific colors, always look for the initial values ​​as we did at the beginning

and can even vary the saturation:

The rest, you know ... our imagination