what does the different colour stand for under stresses tab in post process 1

[Enterprise82]

I am checking the structural stresses in the post process.
I have no idea regarding what the different colour stand for under stresses tab(such as the snapshot in the attachment).
Could you pls tell me the details or where i can find the definitions for these.
Thanks

 

[SethGuthrie]

Positive stresses noted in red, negative stresses in blue. For more on stress sign convention, see Help - Contents - STAAD Graphical Environment - GI Help - Postprocessing mode - pages... - Beam Pages - Beam / Stresses Page