Karkat and Terezi appear to be comfortable enough to make fun of each other without worry that the other will be upset. Karkat trusts Terezi enough with his secret to argue with her, when someone knows a secret of mine I tend to be very cautious around them. They are close! 

Terezi is staying positive while everyone else is waiting to die. While not specifically endorsing Karkat's plan, she is trying to get everyone thinking and active and hopefully get them out of the whole "Let's just wait do die" mindset. 

Karkat is taking initiative, attempting to form a plan to save his friends. 

At this point in time, they are trapped on a meteor. 

Vriska is apparently super important.

Karkat has had a chance to be a hero and a leader, as he says that he saved Sollux's life many times. In these attempts his blood color may have possibly been revealed.