Color vision deficiency (CVD), also known as color blindness, is commonly caused by genetic disorder. Unfortunately, as of 2018, there is not yet a cure for the condition. Contact lenses and glasses with color filter are possible solutions to CVD by applying uniform changes to user's field of view (FoV). On the other hand, optical see-through head-mounted display (OST-HMD) can provide a controllable overlay to user's FoV, which could help for making a better solution. To calibrate colors in FoV of a user with CVD, methods that often used, such as the daltonization process, need light reduce feature, which makes calibrated color darker. However, recent commercially available OST-HMDs don't have a controllable way to decrease the brightness of incoming light. In this paper, we present an approach for light subtraction of OSTHMD using a transmissive LCD panel. A prototype system for achieving a controllable overlay to user's FoV with OST-HMD by using scene camera, user-perspective camera, and the transmissive LCD panel was implemented.