Color of chemicals - Wikipedia
PubChem
Colors of all the elements in the Periodic Table
Brown carbon - Wikipedia
Colors of chemicals - chemeurope.com
Atmospheric Brown Carbon: Sources, Optical Properties, and …
Molecular Composition and the Optical Properties of Brown …
Chemistry of Atmospheric Brown Carbon | Chemical Reviews
Why are chemicals kept in brown bottles - Quanswer
The Chemistry of Colour: A Guide to the Dyes and Chemical World