In fact, depending on your data query you may be able to do this using the Metric output in TSVB that has what is called Color Rules where you can change the background and text color based in the metric value.
In my example I want a ratio between status: OK and status: Error so after switching to the Metric output, in Panel Options I can add the color rules to use 0.5 as my threshold
And in the data use the Filter Ratio metric type for status: OK
And in the options format the number as percent and filter only for documents with any of those values
So now on this dashboard the panel should go to orange if the ratio ever goes below 50%
