Yes they do, they influence people's moods and how they behave. That's why classrooms are painted neutral colours in high schools and bright colours in primary schools.

i've read once that the blue color helps to prevent the effect of the harmful rays coming from our body. concerning psychologically, i think people prefer light clothes when they r happy and dark clothes when they r depressed or sad.

when I get exhausted of my work, I usually turn my head towards the window and look at the soothing green leaves and blue skies... well, they really do change my mood. :)

I think, they do. It helps to remember easily when different sorts of tasks marks by different colors.