I'm a bit confused how this works...I have been working to rig one side and when I turn on "Mirror Mode"...shouldn't I see one half of green verts & one half blue verts? I can't see any vert colors, not even red...

Restart max.

make sure you reset xform before applying your skin modifier.

sometimes if your model is too big ie if your are working in for example cm and the character is

200 cm tall, its can have strange results

lastly try and increase the mirror threshold which defaults to 0.5

Edit: can you see the orange mirror plane helper?

Reset xform (as Ruz says) *AND* re-centre the pivot.

You can do this after skinning, just pop the reset xform under the skin modifier and Collapse To. You may need to toggle Always Deform on the skin modifier after doing this.

Alright thanks guys.

I did a combination of what everyone said so I'm not sure what solved it. Apparently it is working even though I still can't see the colors...(7900 GTX here)

Yep the orange slice plane is still there. But a negative for any red, green, or blue verts still. Odd video problems I guess?