My hunter is level 82, and I had to switch from Blue to Red recently.
~~~For common solo PvE~~~
Up through level 60, Blue was great, Blue was fun... BUT
It feels like Blue fizzles out around lvl 70...
Lothlorien was the last place Blue felt okay.
Mirkwood was so-so
Enedwaith, Isengard, and Great River all got pretty tough for me.
I hate Red, so I delayed switching, even when I ran into big problems. It just becomes hard to handle multiple landscape mobs, or even one elite. Big power issues, some damage issues, and lack of support from legacies. If we're power-leveling, none of this matters, but if we're playing through the game, at some level (70?) I think Blue fails, and we have to switch to Red or Yellow. My other tree is Red, and I haven't tried yellow at high levels yet.
What do you all think?