Public displays, such as liquid crystal displays (LCDs), are often used in urban green spaces. However, these display devices often tarnish the green landscape of urban green spaces due to their artificial materials. We previously proposed a green landscape-friendly grass animation display that dynamically controls the grass color pixel by pixel. The grass color is changed by moving a green grass length in yellow grass, and the grass animation display runs simple animations using grayscale images. In our previous study, the color scale is subjectively mapped to the green grass length. However, this method fails to display the grass colors corresponding to the color scale based on objective evaluations. Herein, we introduce a dynamic grass color scale display technique based on the grass length. We develop a grass color scale setting procedure to map the grass length to the five-level color scale through image processing. In the outdoor experiment of the grass color scale setting procedure, the color scale corresponds to the green grass length based on a viewpoint. Finally, we demonstrate a grass animation display to show the animations with the color scale using experimental results.