Re: customize value hooks - be able to edit color samples in different ways...

[Richard Stallman]

     There are ways to pick a color that are
    simpler, more interactive, and more flexible. Some such color tweakers are
    available here and there in Emacs libraries, but there is no simple way of
    plugging them in, so that Customize can take advantage of them.

Specifying colors is a specialized area.  I think we should
acknowledge that at the outset.  Implementing a convenient way in
Emacs to specify a color would be a nice thing to do, and it could be
used in Customize as well as perhaps elsewhere.

I see no need to worry about hooks for calling this.
Once someone has implemented a nice way to specify a color,
we can make things call it.

    2. More generally, such hooked Customize fields need not be limited to
    colors; the same principle applies to other kinds of values. For example, a
    numeric field might hook to a function that lets you use a slider or a
    DoReMi-style function to adjust the value incrementally.

This focus on how users select among various methods of specifying
certain data is misplaced.  The real issue is to implement a nice
method for various kinds of data.  First let's get ONE such method.
To worry about how we will deal with having more than one for a given
type of data is getting ahead of the game.