Alright
I will attempt to teach you something
this is a picture i randomly chose from my files (most any will do but results will vary)
ok now we are going to make a new layer (layer>new layer) now set the new layer to color colorfill with black
now merge down
NOW, make a new layer and set it to color
use rectangle select and select a portion making sure to leave a border around the edge
and fill with a bright color

repeat until satisfied with the results

and voila!!