There are a variety of reasons why boerewors is not always the same colour. The combination of meat (beef, pork) fat, and spices will vary from recipe to recipe. This will affect the colour because pork is lighter than beef and Worchester sauce is darker than vinegar. The freshness of the meat and the age of the animal also play a role, since an older specimen’s meat tends to be darker than a young one’s. There is unfortunately no hard and fast rule about the colour of the boerewors and the quality thereof.
If a boerewors is made in a consistent way, with consistent raw materials, it should always be the same colour. This is what you should look for. You will then be able to select boerewors that you prefer, rather than wait for a surprise when you get to the braai. When in any doubt, ask your local butcher for his advice in making your choice. Remember, even a supermarket has a butcher on site, who will be able to advise you.