I have already explained the meaning of subtlety and subtle. Both are derived from a Latin word which means “finely woven”--fine spun threads of silk or linen, woven closely together into a strong but very delicate and thin fabric. So when we speak of a subtle distinction we have in mind a distinction that is very slight; as between two tints of yellow. To many eyes they will seem the same; whereas an eye more subtly sensitive to degrees of color can distinguish the difference. We may say of such an eye, that it has a very delicate sense of sight, or subtlety of vision. Subtlety implies delicacy; and when we speak of the subtlety of an artist’s color harmonies--how subtle they are--we have in mind a delicate, exquisite, refined use of color. He has not used many colors; nor obtained his effects by force of strong contrasts. On the contrary, it is by subtle relation of a few colors, by the subtle differences in their values that a harmony, distinguished by its exquisite delicacy, is produced.