A body appears to be of the colour which it reflects; as we see it only
by reflected rays, it can but appear of the colour of those rays. Thus
grass is green because it absorbs all except the green rays. Flowers,
in the same manner, reflect the various colours of which they appear
to us: the rose, the red rays; the violet, the blue; the daffodil,
the yellow, &c. But these are not the permanent colours of the grass
and flowers; for wherever you see these colours, the objects must be
illuminated; and light, from whatever source it proceeds, is of the
same nature, composed of the various coloured rays which paint the
grass, the flowers, and every coloured object in nature. Objects in
the dark have no colour, or are black, which is the same thing. You
can never see objects without light. Light is composed of colours,
therefore there can be no light without colours; and though every
object is black or without colour in the dark, it becomes coloured as
soon as it becomes visible.