Are you referring to cells in a table visualization?
Domo has two types of tables and both can be highlighted in different ways
If the second option sounds like something you want to consider, you might try perusing the Dojo for HTML posts. For an example, in our manufacturing facility we want to call out machine downtime occurrences if they reach a certain threshhold, which we do with the following beast mode:
CASEWHEN `NumberOfDowntimeEventsShift` > 3THENCONCAT('<div style="font-size: 18px; background-color:#e65655; color:#ffffff; width: 100%; height:100%; margin:-40px; padding:40px">', `NumberOfDowntimeEventsShift` , '</div>')ELSECONCAT(`NumberOfDowntimeEventsShift`,'')END