A display device includes a storage unit, a display unit and a processing unit. The storage unit stores a color parameter under a color space. The display unit displays an adjusting interface including a reference color block and a plurality of offset color blocks. When a target offset color block of the offset color blocks is selected, the processing unit updates a color coordinate of the reference color block by a color coordinate of the target offset color block and updates a color coordinate of each of the offset color blocks by a color coordinate of the updated reference color block and an offset value. The processing unit obtains a color transformation matrix according to the color coordinate of the reference color block, the color coordinate of the target offset color block and the color parameter. The processing unit adjusts three output percentages of RGB by the color transformation matrix.