Yeah, Shyamalan makes a contrast between people who take the sentimental approach ( deschanel), those who talk about nothing (wahlberg with the two J boys), those who try to comfort others (Leguizamo), and those who have a sense of humor the whole time (wahlberg with deschanel) My tendency is to always talk about business first, so I would probably be trying to brief everyone on the most important things I think they should know before I'm gone.
As for the water element..maybe the clouds at the beginning? And there's the bath toward the end, where they are sort of letting go of (or washing away) all the unimportant things in their life and beginning to realize what their real priorities are.
As for color, there have been people who mentioned the earthy tones to the clothing of the main characters who survived. And of course there is the mood ring, the color of love, the green effect, etc