I know this may sound like a stupid question but I was curious. We catagorize our colours but how do we know if each individuals sees different or same colours? because we were taught to label them ...
Coloured contacts are mass produced. They generally range in a "medium" diameter to fit everyone. You can only get specific diameters for coloured contacts made in a lab , but were talking big money...and generally that option is only available to people who have a problem-like someone who is born without an iris or has had damage done to it. (the iris is the coloured part).
The size of contact lenses depends on the brand name that you are prescibed for. Your eye dr will pick the brand that best suites the size that you need.