What are golden circles and red circles?

Among the Canon brand lenses, there are a series of lens models with "L" in them, which means "Luxury". This series of lenses spares no expense and uses exquisite materials. The workmanship is fine and the image quality is excellent, but of course the price is very expensive. This series of lenses has a very obvious logo, that is, there is a red decorative ring on the outer end of the lens, which is called a "red ring" lens. Sigma also has a red circle logo, which means quasi-professional lenses. Because Sigma has always made relatively low-end lenses in the lens industry, Sigma’s red ring lenses are also relatively cheap. The same goes for the yellow circle, which represents the professional and non-professional meaning of the lens, as well as the level of the lens. For example, Tamron uses a yellow circle on its head to represent the non-professional and professional lenses.