I quote from Chapter 30 of H. P. Holt’s The Mounted Police of Natal:
...In 1879 the regulation helmet was white, rather high, and had a brass spike with a chain and monogram. There was one trooper who firmly believed in wearing out his old uniform before buying new, so he stuck faithfully to a helmet of an earlier period - a bright blue affair with brass mounts - until the sergeant-major had a brief but decisive chat with him on the subject, and the blue helmet was seen no more.
After a considerable time the white helmet was succeeded by a black one, with black mounts - a distinctly funereal affair; but this was changed before long for a white helmet of the old army pattern, without either spike or chain. The authorities remained faithful to this form of headgear, until the khaki polo helmet was introduced in the year 1898...