If analysis of the natural concept of colour leads to an illusion theory, or to the theory of colours as virtual properties, we still need to develop an account that prescribes how we should, in the future, think about colour, at least in general terms. For practical purposes, it does not matter at all that colours are virtual properties. For these purposes, it is sufficient if "it is as if there are colours"; i.e, these purposes are served equally as well if objects appear to be coloured. They do not need to be really coloured.

There are other, more theoretical purposes for which we need to develop a more comprehensive account of colour, one that specifies other concepts of colour. The best such account is one that sets out a pluralist framework, one that allows for a variety of different concepts of colour, including objectivist and psychological concepts, and arguably, ecological and phenomenal concepts. Moreover, such a framework does not require us to reject the natural or folk concept.

That there is scope for more than one concept of colour should not be surprising. The natural concept of colour is intended to serve a range of purposes. We find, though, that nothing exists that satisfies all the requirements. However, all is not lost. It is possible to develop a new set of colour concepts that as a whole serves all or most of the previous purposes. None of them taken singly serves all, but each serves some. It is built into the natural or folk concept that colours have, broadly speaking, two major roles: (i) colours have a causal role to play in colour perception; (ii) colours serve a variety of epistemological, aesthetic and emotional purposes. Colours serve the latter set of purposes through the way colours appear. Once it is recognised that colours, as specified by the traditional concept, are virtual properties and that there is no property that serves all the functions relevant to that concept, the way is open to recognise two new concepts of colour: dispositional, psychological colour, to take over and consolidate the role served by the appearance, and physical colour, to take over the causal role. Moreover, once it is revealed that the cause of colour perception are complex, it is open for us to see the point of having several physical or objectivist concepts of colour, one framed in terms of microstructural properties, the other in terms of light-related properties.

To argue in this way for the place of a number of concepts of colour, and for the possibility of an objectivist concept, to supplement other concepts of colour, is to argue for a pluralist framework for colours. This framework has the advantage of allowing a place for an objective concept of colour, while not making it mandatory. Whether or not there is any point in having an objective concept, there is, as we have seen, a need for a dispositional concept, one tied to the appearance of colour. The dispositional concept is a crucial part of the pluralist framework.

But once we become enlightened by accepting the theory of virtual colours, how should we then think of the dispositional concept? What exactly does the exercise of the disposition consist in? What exactly is the content of the dispositional concept? The right answer is that there are two parts to the dispositionalist concept. One part refers to the way objects appear, and the other to the feature, whatever it is, which is the causal basis for the appearance. That is, the disposition is not pure but `mixed'. BlueD objects are objects that have some feature by virtue of which they look as if they are blue, i.e., blue in the intrinsic sense, i.e., blue in the virtual-colour sense. To say that this sense of colour is the virtual-colour sense is not to say that colours are ordinarily conceived of as virtual. It is to say that the properties colours are conceived of as being are virtual. The content of the dispositional concept thus presupposes the virtual-colour concept. This means that there is point in retaining this concept, even when we come to know that no objects have the property. The fact that I do not believe that this property of intrinsic blueness is ever instantiated does not mean that I should give up the concept, any more than disbelievers in Satan should give up the concept of satanic.

In this state of theoretical sophistication, my use of the natural concept to describe things requires me to adopt the naive attitude to colour or, preferably, the engaged attitude typical of the playgoer who, at the theatre, suspends his belief that `it is all a pack of lies'. Of course as philosophers, we need to understand why we have this virtual-colour concept and what role it plays, and how it works. But none of that stops me from continuing to employ the virtual-colour concept, whether as scientist, artist, consumer, town-planner, interior decorator or philosopher. As for serving functions such as being signs or as being aesthetically or emotionally significant, virtual colours are as good as real colours.

There is no need therefore to jettison the natural concept. Realising however that the colour properties are virtual properties means that, for our understanding of how such a concept should apply and why it is so beneficial. Part of this understanding is provided by the explanation for why we have the natural concept that we do. The explanation for why the natural concept is beneficial is that the purposes served by the concepts are equally well served if objects merely appear to be coloured and are not actually coloured.