|Metro station in Paris|
The Metro signs in Paris are lovely to be sure. You can tweak a sign so that it stands out by making everything in the image black and white, leaving only the text in color. This process is known as colorization, even though in digital art is done subtractively. You’re not adding color, you’re taking it away.
This isn’t to say that you can’t colorize a black and white photo because you can. This type of colorization is a bit tougher process, but if you watch the colorization video, you’ll find out it’s easier than you think because of the overlay coloring option.
In the above image, I took a shortcut (no layers) in creating the color in the sign (or taking out the black and white). I used the Sponge Tool, which has an option to desaturate. Then, I selected the text of the sign and inversed it (Select>Inverse). The rest was easy. I colored in the entire frame with the soft brush, taking away all of the color around the sign.