We're plotting time-series metrics in the context of network/server operations. The data has a 5-minute sample rate, and consists of things like CPU utilization, error rate, etc.
We're adding a horizontal "threshold" line to the graphs, to visually indicate a value threshold above which people should worry/take notice. For example, in the CPU utilization example, perhaps the "worry" threshold is 75%.
My team has some internal debate over what color this line should be:
- Something like a bright red that clearly stands out from the background grid and data lines, and indicates this is a warning condition
- Something more subtle and definitely NOT red, since the "ink" for the line doesn't represent any actual data, and thus attention shouldn't be drawn to it unnecessarily.
Would appreciate guidance / best practices...