Hughes
This quotation on vibrations will be seen to agree with the laws which I have gained. The fact that six of the notes of keyed instruments are obliged to act two parts, must prevent the intermediate notes bearing a definite ratio of vibrations with the intermediate colours of the spectrum. I name the note A as violet, and B ultra-violet, as it seemed to me clearer not to mention the seventh as a colour. [Harmonies of Tones and Colours, On Colours as Developed by the same Laws as Musical Harmonies2, page 19]