"[Yellow] is the color nearest the light. It appears on the slightest mitigation of light, whether by semi-transparent mediums or faint reflection from white surfaces. In prismatic experiments it extends itself alone and widely in the light space, and while the two poles remain separated from each other, before it mixes with blue to produce green it is to be seen in its utmost purity and beauty.
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As no color can be considered as stationary, so we can very easily augment yellow into reddish by condensing or darkening it. The color increases in energy, and appears in red-yellow more powerful and splendid. All that we have said of yellow is applicable here, in a higher degree. The red-yellow gives an impression of warmth and gladness, since it represents the hue of the intenser glow of fire.
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As pure yellow passes very easily to red-yellow, so the deepening of this last to yellow-red is not to be arrested. The agreeable, cheerful sensation which red-yellow excites increases to an intolerably powerful impression in bright yellow-red. In looking steadfastly at a perfectly yellow-red surface, the color seems actually to penetrate the organ. It produces an extreme excitement, and still acts thus when somewhat darkened."
- Johann Wolfgang von Goethe (1749 - 1832)
Theory of Colours
