A display apparatus includes a display unit, a time setting unit, a detection unit and an image changing unit. The display unit is configured to display a color image. The time setting unit is configured to set a time. The time to be set by the time setting unit can be changed by a user. The detection unit is configured to detect whether the time set by the time setting unit is passed. The image changing unit is configured to change a color image to be displayed on the display unit to a monochrome image so as to warn the user that the time set by the time setting unit is passed, if the detection unit detects that the time set by the time setting unit is passed.