One way to do it is to use the Discrete plugin for Grafana (https://grafana.com/plugins/natel-discrete-panel).
In the Metrics tab, use a query with fill previous or linear.
In Legend tab, check Values, Show Counts.
In mappings, create two range mappings (e.g. From -10000 to N_value Text Normal, From V_value To 10000 Text Alert).
Exit the plugin edit mode and it will reload the states with those you created.
In Color tab, click Add Current Values. Set your Normal and Alert colors as needed.
In Discrete plugin Legend tab, check Values, Show time.
