Image Map changing polygon shapes color

I have a map of North America and each state has the area defined with a polygon. I have a database table with the members in it that I query to see which states have members. If a state has members I need to change the background color for that state. How can I do this when the page is opened in a browser? Is it possible to change the background color in the polygon? Below is a sample of the code defining a state.


Thanks
<map name="Map" id="Map">
<area shape="poly" coords="493,256,472,215" href="#" alt="a" />
<area shape="poly" coords="492,257" href="#" alt="b" />
<area shape="poly" coords="493,255,518,243,496,201,472,215,492,255" href="#" alt="c" />
</map>
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