One place to get started is
this KnowledgeBase entry on changing plot colors, which points to an example of the same.
Another popular method (perhaps because it is or was taught in NI's LabVIEW Basics class) is the notion of making a chart blink when an over-limit condition is detected. You can also do that with a property node by selecting the Blinking property.
If you're asking more generally for advice on handling your data, then you can follow up with more specifics.
Hope that helps,
John