I do agree that colour sense is very subjective. The ability to perceive
variations in colours also varies; I had a friend (not an archaeologist,
fortunately) who could not distinguish different  shades of colour, although
he could see different colours. It made for some interesting clothing
combinations.
 
The Munsell charts at least provide a standard which is widely available. It
is necessary to train and to test people to ensure that they classify colours
 consistently. Until some reasonably affordable, and portable instrument is
devised for objective soil colour classification, Munsell will remain the
best tool for most excavations. It is important, though, to continue to
emphasise the pitfalls and drawbacks which go along with it.
 
Fran Kemmish