IF $class = ($value->status == "done") HOW?

This will also work.

PHP Code:

if($value->status === "open")
  {
    $class = "#536699";  
  }
elseif($value->status === "in_progress")
  {
    $class = "#796699";
  }
else
  {
    $class = "#336699";
  } 


I think that @ivantcholakov suggestion of using a CSS file instead of hardcoded color values is a very good idea. Not that I set a good example of that here