This paper focuses on the design of Helmet-Mounted Display(HMD)digital display interface, which is related to the recognition performance of the pilot. Due to the specificity of the HMD see-through display and the changing backgrounds, there are new demands for forecolor selection. Through experimental means, by taking vernier acuity as a measurement method, and the accuracy and reaction time as the indicators, we made comparison to the relatively optimal values of forecolor symbols under conditions of brightness and saturation of the typical sky background samples. Experimental results showed that: 1) The color HSB value(120° 33% 33%) and(120° 99% 33%) were better recognized under the daytime and all-weather condition;and 2) The color HSB value(120° 33% 66%) was better recognized during the night time. The conclusion provides a scientific reference for HMD aiming interface design.