HI. This is my first time posting here. So, here goes.
Here I'll teach you the basic way to colourize an image with a couple of different styles to make it more interesting.
Style One: Single Colour
1. First, Open an image you want to colorize. Or you can also copy and paste from the Internet. For this tutorial I used a picture of a guy I grabbed from stock.xchng:
2. Create a new layer. You can do this by clicking the tiny square icon next to the garbage can on the Layers window:
3. Click on the Paint Bucket Tool. It looks like this:
Choose any colour that you like (I used dark green #1d6a0e), with Mode: Normal and Opacity: 100%. Fill the picture with the colour selected.
4. Now, to colourize the picture, you need to change blending mode to Color. Do this by Layers > Layer Style > Blending Options. Set it to this:
Or you can do it easier like this:
5. The image you'll get will look something like this:
Style Two: Multicolour
1. Of course, I'm gonna use the same uncolourized image of the guy.
2. Create a new layer.
3. Click on the Gradient Tool:
4. Now, pick a nice multi-coloured gradient. Then, click-and-drag the mouse across the image. You'll get something like this:
5. Change the blend mode to Color. Tada!:
PS: You can experiment with different blends, values, and opacities to get different effects. Have fun!