It is one of the "secrets" of good "design" to use a limited number of _elements_--forms or colours or materials--and to produce _variety_ by skilful and charming manipulation of these.
It is well to follow the early Illuminators in this also: that these few colours be kept constant. When you have chosen a _Red_, a _Blue_, and a _Green_--as pure and bright as you can make them--keep those particular tints as _fixed_ colours to be used for ordinary purposes. For _special purposes_ (pp. 182, 202) paler tints may be made by adding white, and varied tints may be mixed, but even when your work has advanced so that you require a more complex "palette," you should stick to the principle of _constant tints and modes of treatment for regular occasions_: this is the secret of method.
_RED._--Vermilion is prepared in three forms: "_Vermilion_," "_Scarlet Vermilion_," and "_Orange Vermilion_." For ordinary use "_Scarlet Vermilion_" is the best (it may be tempered with a minute quantity of white). "_Vermilion_" is not quite so bright, and tends more to crimson, but, mixed with [p178] "_Orange Vermilion_" it gives the "scarlet" form. The _pan_ colour is generally most convenient.
Where scarlet is in juxtaposition with gold, their effect may be harmonised by having a large proportion of blue in the neighbourhood: sometimes a more crimson colour than vermilion may be used.
_Chinese Vermilion_ is a fine colour, but difficult to obtain; it is even said that the genuine pigment is reserved exclusively for the Chinese Emperor (whose edicts are written with "The Vermilion Pencil").
_GREEN._--Verdigris is a very fine colour, closely resembling, and possibly the same pigment as, the green in early MSS., but I believe that it has not been rendered permanent in modern use.
_Green Oxide of Chromium_ (_transparent_) (or "Veridian") is a very good permanent green. It is rather a thin colour, and requires body, which may be given with _lemon yellow_, or with _white and yellow ochre_; being a rather bluish green, it is the better for a little yellow. This (mixed) green is most conveniently prepared from tube colours.
_BLUE._--_Ultramarine Ash_ (whole tube about 4s.) is a very beautiful colour. It is rather pale and transparent (and a little "slimy" to work) when used alone. A mixture (preferably made with tube colours) consisting of _Ultramarine Ash and Chinese White and (a very little) Prussian Blue_ makes an extremely fine, pure blue. A similar mixture with _cobalt_ as a base makes a very good blue.