The appearance can have color, but inventions and utility models cannot have color or rendering, from the perspective of mechanical drawing.
Another perspective:
Invention and utility model patents protect technical solutions, not solutions. In the technical field, color itself is an electromagnetic wave with a certain wavelength in the visible light spectrum. Each color has a range of bands, which is a range rather than a definite value. If a specific wavelength band has special technical significance, it is necessary to use wavelength to represent the technical characteristics, rather than simply saying: red. Compared with inventions and utility models, appearance design essentially protects a design solution and does not require technology. This is where the addition of color is allowed.