The energy bar will change color based on your current RtB procs using a weighted score system. Put simply, if your energy bar is green then it's a very good roll, yellow means average, and red is a bad roll.
The values that I have set by default are below, you can edit them by going into the Custom Options tab and changing the numbers around.
Score:
50+ = green
25-49 = yellow
1-24 = red
0 = gray
Broadside = 50
True Bearing = 50
Ruthless Precision = 25
Skull & Crossbones = 25
Buried Treasure = 12
Grand Melee = 12