How to count pixels of a specific color

I was recently asked how can I count the number of pixels of a specific color in a photograph.  I found this to be a little tricky but doable.

• The solution is to zoom into the area of the color you want to select. 
• Use the Magic Wand tool and set the tolerance to 1.
• Select Similar
• Open the Histogram panel

Here you will see the information about the total number of pixels that have been selected. In this case there are 781.