The use and importance of salt on Gor

Salt is needed for medicines and antiseptics
Salt is needed for preservatives (With no refrigeration on Gor this is quite important!)
Salt is needed for bleaches and cleansers
Salt is needed to make bottle glass and tanning chemicals
Tahari salt accounts, in its varieties, I would suspect, for some twenty percent of the salt and salt-related products, such as medicines and antiseptics, preservatives, cleansers, bleaches, bottle glass, which contains soda ash, taken from salt, and tanning chemicals, used on known Gor. Salt is a trading commodity par excellence.
Tribesmen

There are areas where salt is used as money, it is that precious and important
There are areas on Gor where salt serves as a currency, being weighed and exchanged much as precious metals. The major protection and control of the Tahari salt, of course, lies in its remoteness, the salt districts, of which there are several, being scattered and isolated in the midst of the dune country, in the long caravan journeys required, and the difficulty or impossibility of obtaining it without knowing the trails, the ways of the desert.
Tribesmen

Salt is an important trade commodity and is taken in raids at times
Salt, incidentally, is obtained by the men of Torvaldsland, most commonly, from sea water or from the burning of seaweed. It is also, however, a trade commodity, and is sometimes taken in raids. The red and yellow salts of the south, some of which I saw on the tables, are not domestic to Torvaldsland.
Marauders

Salt in Torvaldland obtained from sea water or burning sea weed
The colored salts of the south are imported
Salt, incidentally, is obtained by the men of Torvaldsland, most commonly, from sea water or from the burning of seaweed. It is also, however, a trade commodity, and is sometimes taken in raids. The red and yellow salts of the south, some of which I saw on the tables, are not domestic to Torvaldsland.
Marauders

Red salt of Kasra comes from Klima via kaiila caravans to be exported from Kasra
"This is Ibn Saran, salt merchant of the river port of Kasra," said Samos.
The red salt of Kasra, so called from its port of embarcation, was famed on Gor. It was brought from secret pits and mines, actually, deep in the interior, bound in heavy cylinders on the backs of pack kaiila. Each cylinder, roped to others, weighed in the neighborhood of ten stone, or some forty pounds, a Gorean "Weight." A strong kaiila could carry sixteen such cylinders, but the normal load was ten. Even numbers are carried, of course, that the load is balanced. A poorly loaded kaiila can carry far less weight than one on whom the burden is intelligently distributed.
"Ibn Saran, in the past months, has heard an unusual thing," said Samos. "I leaned of this from a captain, one known to him, with whom he spoke recently upon the salt wharf." Samos was first in the Council of Captains of Port Kar, which body was sovereign in the city. There was little of interest, which did not, sooner or later, come to his attention.
Tribesmen

White salt from Klima makes up most of the salt exported.
Most salt at Klima is white, but certain of the mines deliver red salt, red from ferrous oxide in its composition, which is called the Red Salt of Kasra, after its port of embarkation, at the juncture of the Upper and Lower Fayeen.
Tribesmen

Yellow salt
The red and yellow salts of the south, some of which I saw on the tables, are not domestic to Torvaldsland.
Marauders

Salt from Klima is divided into nine qualities, each cylinder marked with the quality of salt it contains
The salt is divided into nine qualities. Each cylinder is marked with its quality, the name of its district, and the sign of that district's salt master.
Tribesmen

Several quotes through the books mention "colored table salts", which could refer to the white, red and yellow salts mentioned, or could also possibly mean more colors existed.
That would not be far-fetched as salt crystals on earth come normally in white, but can be found blue, purple, pink, yellow and gray.
SOURCE - Halite (Sodium Chloride)