You can try core Table widget's cssClass property function:

https://www.koolreport.com/docs/koolphp/table/#table-settings-cssclass-options

//Use function
Table::create(array(
    "cssClass"=>array(
        ...
        "td"=>function($row,$columnName){
            return "cell-css-class"; // return a css class by $row[$columnName] value, then assign a font color rule for that css class
        }
    )
))
 

If you have any question let us know.