Variations in the electromagnetic wavelengths of absorption and reflection of molecules do not only make life colorful but also are often of central importance in solar energy conversion and optoelectronic information processing and transfer. Dithizone and its derivatives and complexes are, to our knowledge, probably the most “colorful” compound, being responsive to no less than seven different external stimuli that effect color change. Apart from a more detailed discussion of the cyclic voltammetry and observed electrochromism in the SCH₃-substituted free ligand and mercury complex, concentratochromism, solvatochromism, halochromism, thermochromism, and chronochromism in the ligand, and photochromism in the carboxy-functionalized phenylmercury(II) complex are also presented here. Color changes are either associated with proton transfer or loss, or isomerization.