Although single color tones are expressive, they seldom exist alone in works of art. Significant expression requires variety. The invention of original and expressive color combinations is a rare gift of genius. Rough rules of color combination have been devised from the practice of artists and from experiment, the following of which will enable one to produce faultless patterns, but without genius will never enable one to create a new expression. Color combinations are either harmonious or balanced, the former produced by colors or tones of colors very close to one another, the latter by the contrasting or widely sundered. In the one case, we get the quiet commingling of feelings akin to each other; in the other, the lively tension of feelings opposed. Compare, for example, the effect of a Whistler nocturne with a Monet landscape. The colors that do not go well together are such as are not close enough for union nor far enough apart for contrast. They are like personalities not sufficiently at one to lose themselves in each other, yet not sufficiently unlike to be mutually stimulating and enlarging, between whom there can be only a fruitless rivalry turning into hate. Such are certain purples and reds, certain greens and blues. Yet, through proper mediation, any two colors can be brought into a composition. All colors are brought together in nature through the sunlight, and in painting or weaving by giving to rival colors the same sheen or brightness. Or again, the union may be effected by combining the two with a third which is in a relation of balance or harmony with each, as in the favorite scheme of blue, red, and green. Despite their ability to express, colors cannot stand alone; they must be the colors of something, they must make line or shape. Lines, on the other hand, seem to be independent of color, as in drawings and etchings; yet there is really some color even there--black and white and tones of gray. That color and line are independent of one another in beauty, is, however, shown by works, such as Millet's, which are good in line but poor in color. Lines have, as we have already seen, the same duality of function as colors: they express feeling directly through their character as mere lines and they represent objects by suggesting them through resemblance.