Or do they just make a photo greyscale and recolor it? o_o
I want to color eyes funny colors.. xD

Well you can get them anywhere really or make them B&W on your own. I usually just go to Blend Challenge sites or here.
http://www.bwgreyscale.com/

Well what I do is take a colored picture and duplicate the layer. I then make the duplicated layer greyscaled and erased the parts of the picture that I want in color. It works :]

I just put a normal colored picture on a layer then create a new layer and turn it completely black. then i click on color in the scrolly thing that says normal.. then erase the parts on the black layer that i want to be in color :]

Many peopl use model photos to colorize since the quality is better and the photos are often more interesting to do.

http://community.livejournal.com/foto_decadent/
http://www.bwgreyscale.com/
http://www.elegancepixelfied.com/
http://anxietykills.org/mirror/cpg142/index.php
http://herfamedgoodlooks.com
http://supermodels.nl

So, yes. You can desaturate the image and enhance it by using the Curves and/or Levels functions in Photoshop.

Some tutorials on how to colorize images can be found here. Have fun.