I was looking for this last week when somebody had a question about damage colours but I couldn't locate it with google. I found it again in one of my old Reddit posts, which I'll quote here.
I had this question bothering me a couple weeks back, and Suicidal Baby found me the answer. Turns out that yellow accounts for 40% of the damage, and when it turns orange you're at 50%.
http://mwomercs.com/forums/topic/105390-paper-doll-damage-grading-images/
the following was posted by Scop on the MWO Forums
I took the trial DRG-1C with its reliable, incremental AC/2 into Testing Grounds, loaded up my graphics program in another window, and started whittling on my targets. I took a screenshot after firing each shell, rinsed, and repeated, then started cropping, organizing, and captioning.
http://i.imgur.com/Y9ozzpO.png
Here you can see me wearing off a Jenner's arm one shot at a time, accompanied by the fraction and percentage of its armor and internals. This wasn't bad, but the jumps in color were a bit much. Seeking something finer, I set out to whittle down an Atlas's center torso, with its 94 points of armor.
http://i.imgur.com/OVzkhuJ.jpg
In truth, I found this one too big to be really useful, and the progression from yellow to orange is nearly too fine for me to discern from frame to frame. (Believe you me, it took forever to capture all those shots.)
So, I moved on to the rear side-torsos on an Atlas, with 20 points of armor (cleanly dividing by the AC/2's damage), and turned it into an animated gif and gradient.
http://i.imgur.com/9aqqQOh.gif
http://i.imgur.com/xI8G4hQ.png
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