TV has lost its color?

Ive had my tv for about 4 years I think its Best Buys model off the floor and the other day without me doing any thing it went to black and white and I cant get it back to color Ive try unplugging it nothing, messing with the settings nothing so I dont know what to do the on/off and volume are still in color I dont have the owners manual because I got it open box.