Set icon of button to a graphic

[Bill Vlahos]

I want to show if an object is either too hot, too cold, or within 
normal temperature range? I was thinking that a simple circle filled 
with green, blue, or red with the temperature next or under it would be 
an easy way to tell at a glance if things are normal. I was thinking 
that if I create a button with the icon set to one of the 3 images and 
setting the label of the button to the temperature would do the trick. 
I would simply set the icon of the button to one of the three "colors".

I created a 3 small circle graphics (one with each color) but I can't 
seem to select those for the button icon as they are a "graphic" not an 
"image".

How can I convert a graphic to an image?

Bill Vlahos