While looking around for an addon that could display castbars (for my own character, not for enemies) I came across people talking about yellow and red rays coming from mobs, Yellow being a tell for a blockable attack and red for an interuptable.
Now, I've never ever in my 70 + hours in game seen these rays. (not talking about red cones/circles for cleaves/aoe) After reading about them I even let a boatload of mobs beat the crap out of me while staring at them just to see if there really wasn't anything i'd missed. Now in the options there is a line called 'Combat Cues' that's off and greyed out, is this the option that would make those rays appear? And if so, why can't I turn it on? Or do these rays simply not exist and are the people talking about them just confused?
(Here's the thread where people were talking about them:
http://forums.elderscrollsonline.com/discussion/69155/why-no-cast-bar/p1)