The selection of pigment carbon black can be based on coloring characteristics or physical properties. The choice of varieties for coloring purposes is primarily determined by the required darkness of the finished product. Extremely high darkness requirements can be met with finely divided pigment carbon black; products like PE garbage bags, plastic bags, and cable materials, which only require a moderate level of darkness, can use carbon black varieties with lower specific surface area and higher structure. Microscopic errors in the measurement and mixing of carbon black during plastic coloring can lead to significant color differences, so it is advisable to use larger particle size, lower coloring strength, and low pigment carbon black. This allows for slightly higher carbon black usage, smaller measurement errors, and advantages such as better dispersion and lower cost. For gray plastics, fine-grained pigment carbon black often results in a brownish gray, while coarse-grained pigment carbon black produces a bluish gray.