In this article I'll be noting some of the links that have been made regarding sulfur and red hair.
(The illustration L'Ame du vin by the artist Carlos
Schwabe, supplanted by the alchemical symbol for sulfur)
Red hair is said to have a high sulfur content in relation to hair of other colours. Over the years people have speculatively argued that this may bear some relation to the perceived fiery temperament redheads are said to have. As well as other possible personality traits.
Sulfur can often be found on the edge of volcano craters and for this reason was traditionally called brimstone in English. This brings to mind Christian notions of "fire and brimstone", and perhaps may help explain why red hair is sometimes associated with Judas and devilish behaviour. However, brimstone was also burned by adherents of the Greek Orthodox Church to ward off evil and disease. So in some ways such traditions regarding sulfur can be seen more positively as acts of purification.
In alchemy sulfur is also highly regarded and is often viewed in tandem with mercury. In fact, mercury, sulfur and salt are viewed as being the three most important constituents in western alchemy. Mercury is associated with the Moon, the feminine and water. Sulfur associated with the Sun, the masculine and fire. The combination of the two creating the symbolic alchemical marriage between the Sun and the Moon. Salt then being said to symbolise the fixed and permanent Earth.
As for the possible relationship between hair and temperament Rudolf Steiner had this to say;
Equally you can learn a great deal from one hair of a human being. But here you must remember how different, how individual is the hair of each person. Some of you are fair, some of you have black hair. What underlies this? Those of you who are dark have in the blackness of the hair an iron process which is going on in the hair. Blondeness comes from a sulfur process which is particularly strong in those people who have red hair. These things are of the very greatest interest. I have actually known people of whom it could be said that they were really fiery, with their bright red hair. A very strong sulfur process is present here, whereas in black hair there is a comparatively strong iron process. You must remember that this emanates from the whole human organism. A person who has red hair is always producing something that is a highly combustible substance - sulfur - and his hair is permeated with it. The other person who has black hair secretes iron - a substance that is not combustible but of a different character. This reveals a deep-seated difference between the two people in their whole organization. In individual cases, much can be learned about the whole human being from the kind of hair he has.
It'll be interesting to see if anything else comes to light regarding all this.