CHANGING THE COLOR OF CELLS IN A DW TEMPLATE

A better question is why are you using TABLES? 

Tables are for displaying tabular data in columns & rows like charts & spreadsheets.  We don't use them for web page layouts.  That's all done with CSS now.

You'll need to create a class in your stylesheet with a background-color of your choosing, for example....

.blue_bg {
background-color:blue;
}

Then select the element you want to add it to, in Live or Design View, and choose it from the class dropdown menu in the Properties Window...

I cannot recollect any of the DW Templates having cells, let alone cells with colour. Please enlighten me.