Sentence:  The colours primary in themselves are the colours white and black; the colours truly <WSD>mediary</WSD> are blue, gold, and red; the sub-mediary colours are green and any Similar if there are any. 
Meaning of the word marked with <WSD> tags:  (of color) Having a primary hue (red, blue, or gold), as opposed to one that can be created by mixing colors with primary hues.