In this exercise we learned how to decrease the color depth in a 16 million color image.
This is useful when you want to turn a .jpg into a transparent .gif.

In this exercise I made a button then reduced the image color depth size several times.
I left the canvas white so that the differences could be seen. I think the 256 is best.

A transparent .gif , which if you've noticed I use a lot of, is a .gif image that takes on
the background of what ever it's placed on. At least that's the way I interpret it. My
instructor will correct me if I'm wrong.

Notice that the green background can be seen through the light blue of this .gif.   Neat huh.