Portal 2 : Can you switch cross-hair portal color ? (For lefties)

GlaDOS seems more interested in dividing Blue and Orange than picking favorites, and will show favor to either Blue or Orange. In the Yogscast, GlaDOS awards Orange "five science collaboration points" in one level (10:27 in), then awards the same to Blue in a later level (11:45 in):

In a later episode, GLaDOS states that:

• the challenge would present a challenge for one of the two given one's performance so far, but doesn't say who (0:00)
• the two form an excellent partnership with one handling the cerebral challenges and the other "ready to ponderously wander into action should the test suddenly become an eating contest", again doesn't say who is better (5:28)

But the smoking gun, as it were, that she doesn't necessarily favor Orange comes at 9:00 when she states:

To reiterate, this is not a competition. Still, if it were, Blue would be winning. [inaudible] Blue receives five science collaboration points.

So whether it's dependent on performance is possible (although unlikely if you watch these videos), but she doesn't seem to have a complete disdain for Blue.

When you go into the entrance for a co-op zone, there will be a little bar graph and lights for each player (blue and orange) that show which of the maps they have completed.