This is the color the mob's name is displayed in when you mouse-over or target it.
Most enemies you will encounter will be of Normal rank. Other ranks are progressively harder and may require companions to deal with them (assuming the encounter is White to you).
The color of the Health Bar indicates the aggressiveness of the creatures stance towards you.
When you move your mouse over a mob there is some information there for you. Not much but think of it as your early warning system. First is the name of the mob in a color that indicates it's level relative to your own (Consider Color, above). To learn the actual level you have to target it and look at the portrait. Second is the mob rank, such as Normal, Signature, Elite, Elite Signature, etc. The mob's Health Bar appears below this and the color indicates its stance towards you.
When you target a mob its portrait appears on your UI to the right of your own portrait. There are several bits of information here to help you. Below the portrait is the mobs level. The Morale and Power are indicated in standard bars to the left. Morale Bar color indicates Stance. the styling of the ring around the portrait indicates the creatures Rank but this is much easier to determine on the mouseover tooltip.
Have you ever wondered just exactly what the runes on the target reticule say? It was certainly one of my first questions!
You see, when I was about 9 my uncle David came to visit one summer and, each night, he read The Hobbit to me. He almost finished it before he left, but he left me his copy. I finished it soon after and for my next birthday he gave me the original 3 paperbacks from Ballentine Books of The Lord of the Rings. These were the ones that had the covers that were cut from a single painting (I had the 6' poster of it on my wall for many years).
It took me almost 2 years to read LotR the first time. All of 5th grade for the Fellowship, 2 months in the summer for The Two Towers (I did not play outside much that summer) and about the first semester of 6th grade to finish Return of the King.
Well, this morning I opened up my hard-bound Houghton Mifflin edition of RotK to the Angerthan table and found the 6x8 note cards with my original notes on the translation for Angerthas Moria (the version used by the dwarves of Moria) and the slightly more eclectic Mode of Erebor.
Using Angerthas Moria I tackled the translation. My first pass thru did not make much sense to me, as whoever did this at Turbine chose to convert the message phonetically first, then encode it in the runes. The first 2 words were gibberish to me, rendering as "ghw e" and "hw u n" and I stared at it for quite some time, checking and rechecking my notes. Of particular concern was whether the first rune was #26 (w) or #11 (dh). I finally decided it had to be #11 and, by saying the phonemes quickly over and over I finally realized the message.
"dh e(eh) hw u nj--n th a t i(y) s ch o s--' e n"
The One That Is Chosen