White balance has a big impact on the tone of the display so it is important to keep the same white balance in different brightness at the same configuration. Figure 2-13 shows the color shift which is easily captured in in ultra-low brightness. the difference in parasitic capacitance between lamps of different colors is the main reason. Generally the Blue LED has much more parasitic capacitance than the red LED.

Figure 2-13 Color Shift in Low Gray Scale