A Broker Data Source based on the Vengeance buff for all tanking classes. Requires a Broker display add on.
LDB-Vengeance displays the current AP value that your Vengeance buff provides.
Optionally it will show the maximum possible value and the current percentage of that. Options can be configured using Blizzards addon interface options.
So far there is no colored display. The tooltip is meaningless.
Note
The only DataBroker I have used thus far is ChocolateBar.
Credits
To Dridzt for Vengeance Status – which gave me an initial idea how I could detect the vengeance buff, and how to check for the value
To Shackleford for LDB-Threat – I had no clue how to write a data source