For each column you need to write a proper renderer function in JS.
function OnReconfigure(sender, store, colModel)
{
colModel.getColumnById(1).renderer=function(val, metadata, rec, row, col, store) {
if (row==0)
metadata.attr='style="background-color:green;"';
return val;
};
colModel.getColumnById(2).renderer=function(val, metadata, rec, row, col, store) {
metadata.attr='style="background-color:green;"';
return val;
};
}