what is the significance of yellow color?

Answer 1

It signifies jealousy and deceit, among other things.
See also http://www.factmonster.com/ipka/A0769383.html (look for Yellow down the page)

Answer 2

it depends on the context in the book. no colour has a significance in and of itself, unless it is the racially signifying terms of black and white...

Answer 3

It's often used to signify Asians.

Answer 4

it makes people feel happy and gives you a warm feeling