C is for Colour (or Color)
Among my scientific illustrations are several colour mixing graphics:
ADDITIVE (light) colour mixing
SUBTRACTIVE (ink CMYK) orthographic
SUBTRACTIVE (ink CMYK) inks pouring from tins
GRAPHICAL OPTICS (eBOOK)
OPTICS images on framed prints, gifts, and cards
COLOUR MIXING GRAPHICS to licence for publishing and business