The notebook WebSafeColors.nb defines the functions 
WebColorsPalette[] and WebColoringPalette[].

The function WebColorsPalette creates a palette that, 
when clicked on,  pastes the desired RGBColor directive 
into a notebook. 

The function WebColoringPalette creates a palette that, 
when clicked on, will color your selection with the 
desired web safe color.

Also included are the palettes that are generated by 
these functions: WebSafeColorsPal.nb and WebSafeColoringPal.nb
respectively.

The palette WebColorsPal.nb has two buttons that
generate these two palettes.

The functions WebColorsPalette[] and WebColoringPalette[]
and the palette WebColorsPal.nb require Mathematica version 
4 or later. The two palettes WebSafeColorsPal.nb and 
WebSafeColoringPal.nb should work with Mathematica
version 3 or later (though I haven't tested them with
that version).