We're gonna start off with this desaturated image from Serial Experiments Lain. This tutorial works best with desaturated images. To desaturate your image go to Image>>>Adjustments>>>Desaturate. But this tutorial works with colored images too.
Now, Layer>>>Duplicate. Select the Regular Brush tool. There should be a few pre-installed brush sets in your Photoshop Installation, we're gonna select the
Basic Brush Set. Now select the brush at the very bottom of the preset (sizes will vary depending on image size).
Make your values like this:
Click
Now, select colors of your choice to colorize the image,
only click the brush tool, DO NOT DRAG IT! Your image should look like this now, weird huh?
Now go to Layers>>>Layer Style>>>Blending Options>>>Screen. And your image should now look like this:
There are other variations you can use to color the image, here're two more you might like.
Layers>>>Layer Style>>>Blending Options>>>Overlay
Or, Layers>>>Layer Style>>>Blending Options>>>Color
And that's how your give your images that nice color!