Using the colorizing tool you can change the picture to any color, make it black and white, darken it, lighten it, etc.

Open up the picture you want to colorize. Here's mine:



Go to the Colors menu at the top > Colorize.



Above shows you how to make your image black and white. Move the bars back and forth to change it to different colors, darken it, etc.

If you need any help - ask me here.