Blue-gold is a combination of dark blue and gold. According to the color theory: blue+yellow = green. Showing the effect of rich texture and noble feeling. Due to different light and materials, the specific color presentation will be different. Frequent use of RGB system has a great influence on photography. The core concepts of RGB system are three primary colors: red, green and blue. In this system, red plus green equals yellow, yellow plus blue equals cyan, and blue plus red equals magenta. The three colors of yellow, cyan and magenta are added together to get white, so the RGB system can also be called "additive color system". The three primary colors in this system are red, yellow and blue. The difference of color purity will greatly affect the color. Hue is a word in the field of art. In fact, in a sense, it is the tendency of colors, such as green, blue and red, which are all different shades.