I don't know of a direct way to do this in LabVIEW, but there's a pretty good example in the NI Developer Zone Resource Library that demonstrates how to fake it using multiple plots.
Do a search in the Developer Zone for "changing the plot color", and the first hit should be the example I'm referring to.
Another popular option is to use an attribute node or property node for your chart to cause it to blink when a plot goes above a particular limit.
Regards,
John Lum
National Instruments
