What is the psychology of notification colour?
It is all about attention and reaction time: Information are coded in visual, aural and tactile channel. Here you have primer of visual coding. Visual coding could be signs or text.

You have shorter time of reaction to primary colors (red yellow blue) and there is some kind of international standard which determine meaning of colors ( red-stop, green - walk... etc...) That is the reason why red.

I recomend you that you read some text in visual sensory perception, measuring time reaction, and some book of ergonomics psychology.

EDIT: Literature:
http://hfs.sagepub.com/content/17/6/542.short

http://www.who.int/fctc/guidelines/ArtElevenWogalterNine.pdf

EDIT2: Here are lot about reaction time:
http://biae.clemson.edu/bpc/bp/lab/110/reaction.htm