"But this discovery is by no means confined to colours as they exist out of the mind, either in the rays of light, or surfaces of bodies; but is equally true of the ideas of colours in the mind itself: for it appears, by experiments, that the idea of red and the idea of yellow, confounded in the mind by co-existence or rapid succession, make the idea of orange; the ideas of blue and yellow, that of green. &c. and those of the seven simple colours that of white."
An Essay on the Vital and Other Involuntary Motions of Animals
3 entries in ESTC (1751, 1763, 1768).<br>
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Robert Whytt, <u>An Essay on the Vital and Other Involuntary Motions of Animals</u> (Edinburgh: Printed by Hamilton, Balfour, and Neill, 1751). &lt;<a href="http://books.google.com/books?id=eCz7KJ_6XYIC">Link to Google Books</a>&gt;