In the thread below is a slightly more advanced example where we do multi-coloring related to how many days overdue a task is, but you could use the same principles in your case.
What’s shown there is how to set the class within a cell using <span>, and then using CSS to style the entire cell.
You could also use a simple variant of just presenting the <span> with some color settings, but that would then only affect the actual text within the cell, not the entire cell.
Given the CSS is stored into a snippet, which you’ve enabled, you should be able to replace the last column of yours for reviewed with:
choice(reviewed,
"<span class='cellOK'>OK</span">,
"<span class='cellVERYLATE'>No</span>") as Reviewed