Human beings use colour to manipulate their personal appearance and environment. A large part of this usage falls within the area of oral tradition and ritual that have been handed down within families, tribes or geographical areas. The resulting images are part of our culture; the), are activities that give its feelings of belonging and of doing the 'right thing'. Two surveys were designed to learn more of these very human activities. The first centered on Britain and Ireland; the other was international. Three major driving forces were found for the use of colour in folklore and symbolism-economic, historical and social. The Principle of Adaptation of Physical Resources accounts for the choice of mounting colours of most countries. Colour usage in death echoes the three approaches to mourning of sadness, joy (for the life of the dead), and fear of the spirits of the dead. The Principle of Adaptation of Ideas accounts for regional variations in colour folklore. This embodies a Darwinian-type principle of behavior, that is, "to survive within a community a belief must have relevance to that community." A major principle of folk medicine involving colour is the Principle of curing like with like. There are four Principles of Colour Selection in folklore-by the contrast displayed, as a transfer from the perceived or actual usefulness of the colour, by association, and by availability. Green above all colours has especial significance both in the UK and Ireland. In everyday language it is the Principle of Singularity that controls use of colour words as symbols. The biological mechanism permitting these many and contrasting uses of colour depends on the fact that colour is a perception, not the property of an object. That is, a colour can 'mean' whatever we wish it to 'mean'. (C) 2003 Wiley Periodicals, Inc.