...where, in a dark room, an aperture of air and also an aperture of candlelight fall upon the object, and in such a place their differences will certainly be seen clearly and distinctly. But without such a comparison their difference will never be recognized, except for the colours that have the greatest likeness; yet these will be recognized, such as white from pale yellow, green from blue; because, the light that illuminates the blue being yellowish, it is like mixing blue and yellow together, which compose a fine green; and if one then mixes yellow with the green, it becomes more beautiful.

[249] Of the colours of incident and reflected lights. L A, folio 19. a.
When two lights place the shadowed body between themselves, they cannot vary except in two ways, that is, either they will be of equal power, or they will be unequal, speaking of the lights among themselves; and if they are equal they can vary their splendour upon the object in two further ways, that is, with equal splendour or with unequal: equal it will be when they are at equal distance, unequal at unequal distances. At equal distance they will vary in two further ways, that is, the object will be less illuminated by the equal lights in splendour, and in distance 3 the lights equal in power and equal in distance 4 from the object opposite.
L A, folio 19. b. The object situated at equal distance between two lights, that is, equal in colour and in splendour, can be illuminated by those lights in two ways, that is, either equally on every side, or unequally. It will be equally illuminated by those lights when the space that remains around the two lights is of equal colour and darkness or brightness; unequal it will be,