have you tried pressing said button to change it back to the color that worked?
perhaps either you turned off the lights, there is a problem (short?) within the blue segment or the led panel burned out. led's don't typically burn out quick so i'm thinking either the unit is off or theres a circuit problem. pop the front cover off and look if pressing the button doesnt help.
Thanks ssddx for the suggestion. I have tried pressing the button and nothing happens. You may be right about there being a circuit problem I will try to figure out how to work on that.