It is wrongly supposed that the art of arranging colours so as to produce the best effects in printing is entirely dependent on the taste of the operator; for harmony is determined by fixed natural laws. The increasing demand for decorative or ornamental work renders it of some importance to the letter-press printer to make himself acquainted with these laws; as, without some attention to them, the most elegant designs of the type founder, and the finest inks that can be made, may yield but an indifferent, if not a decidedly unpleasing, result. The following remarks will be of use to persons to whom the subject is new; but for a thorough explanation of it they should refer to Chevreul on _Colours_,—a valuable work in the French language, which has been translated into English. I. We may, in the first place, consider WHITE LIGHT as composed of three primary colours—blue, red, and yellow—duly blended; these three, in an infinite variety of proportion, serving to produce all the hues in creation. If we take any two of these primaries and mix them, we have a _secondary_ colour. Thus, blue and red form _violet_, blue and yellow give _green_, red and yellow make _orange_. Each of these secondary colours harmonizes perfectly with the primary which does not enter into its composition. Violet, for instance,—itself a mixture of red and blue,—harmonizes with yellow; green, having no red in its composition, agrees well with red; orange, in the same way, forms a perfect contrast with blue. Either of these contrasts has the effect of mutually brightening the colours employed; a red and a green, &c. being more beautiful when placed side by side than when viewed singly. This is termed the HARMONY OF CONTRAST OF COLOURS; and a good example of it is seen in the scarlet geranium, or the holly; the one showing a light green leaf opposed to a bright red flower, and the other a deep green leaf with a dark red berry. The _mixing_ of colours is a very different thing from _contrasting_ them; for strange as it may seem, although one combination of the primary colours gives _white_, yet another proportion will produce _black_. While, then, red and green look beautiful side by side, it does not generally answer to print red ink on _green paper_. The reason is, that as the ink is slightly transparent, some of the green shows through it, and appears somewhat black, and thus lowers the brilliance of the red in the same degree as so much black ink would, if mixed with it. This remark will apply to orange or yellow on a blue paper, &c. The darker and fuller the body of colour used, the less it is affected in this manner.