Dynamically Changing Background Color

I'm having a problem dynamically changing the color of a table background.

I'm not sure exactly how to word this, but I'll give an example.

I have a function called greentored(propname)

i want to be able to change the following to a different color:
document.all.propname.style.visibility

but substitute the propname with the variable that I'm sending over.

Here is what I had written before but it did not work, it should be easy to
understand what i'm trying to do:

function greentored(propname) {

changecolor = "document.all." + propname + ".style.background";

changecolor = "green";

}

I understand why this doesn't work because all i'm doing is reasigning
"changecolor" to equal green, rather then setting the property of the first
instance of "changecolor" to green.