And if one look through a prism upon a white object encompassed with blackness or darkness, the reason of the colors arising on the edges is much the same, as will appear to one that shall a little consider it. If a black object be encompassed with a white one, the colors which appear through the prism are to be derived from the light of the white one, spreading into the Regions of the black, and therefore they appear in a contrary order to that, when a white object is surrounded with black. And the same is to be understood when an object is viewed, whose parts are some of them less luminous than others. for in the borders of the more and less luminous parts, colors ought always by the same principles to arise from the excess of the light of the more luminous, and to be of the same kind as if the darker parts were black, but yet to be more faint and dilute.

Isaac Newton

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