A video pre-amplifier for increasing OSD signal colors in a display device and a method thereof includes an OSD interface block, a video signal amplifying block, an IIC bus control unit, and an intensity control unit. An OSD interface block receives the R, G, and B OSD signals, modifies, or levels, the R, G, and B OSD signals in response R, G, and B control signal, and outputs the leveled R, G, and B OSD signals. A video signal amplifying block synthesizes the leveled R, G, and B OSD signals with the R, G, and B video signals, respectively, amplifies the synthesized signals, and generating R, G, and B output signals. An IIC bus control unit controls the interface between a microcontroller and the video signal amplifying block in the display device and generates a predetermined mode signal. An intensity control unit generates the R, G, and B control signals based on combinations of bits of the mode signal and a predetermined intensity control signal. Using the video pre-amplifier and the method of increasing the OSD signal colors, an increase in the number of output pins of the OSD processor and the number of input pins of the video pre-amplifier can be minimized, and an increase in the number of the OSD signal colors is possible.