Assuming the dashboard is using SimpleResultsTable , this doesn't appear to be possible via CSS alone.
Custom Event Renderers will add a CSS class when using an EventsViewer module, but not when using SimpleResultsTable -- they render individual events, not results.
I have an open question along these lines as well:
http://answers.splunk.com/questions/6698/heatmap-style-overlay-at-row-level
You would need to be able to add a CSS class the <tr> tag and/or each <td> tag in the row. The difficulty is in adding a new CSS class based on your "trigger" value in that row. Once you have the class tag, the CSS is easy via application.css or by assigning a stylesheet in the view definition.
The two approaches I know of are:
Use JavaScript to check each row and add a given CSS class to each cell in the row, based on the value of the cell you're using to trigger colorization.
Customize or replace the SimpleResultsTable module to add the needed CSS classes.
Neither is particularly elegant. Unless someone offers a better way, this would be a great enhancement request. I've had some (very limited) success experimenting with the second option.
If you are using EventViewer to view individual events, then Event Renderers may be an option.
The default CSS approach shown here never worked for me as shown, possibly because I haven't tried it with custom HTML, or possibly because of the particular CSS elements I was trying to use.
If you don't see anything happening, consider using Firebug to verify that the CSS class is really being added, and to see what the CSS heirarchy should look like. You may need to adjust CSS paths, for example:
.splEvent-FreeSpaceGreen table tbody tr td .event em {
color: #00ff00;
}
You can use the CSS Reloader plugin to make it easier to preview CSS changes as you make them.
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