Cataract brunescen results due to deposition of-
"Nuclear sclerosis also distos color vision because of-yellow-brown urochrome pigment, chich accumulates in the lens and filters blue wavelenths of light". Older nuclear cells lose organelles and cell membranes, with increasing density and dehydration dnd accumulation of yellow urochrome pigment (possible photo-oxidation product). When advanced, it becomes brown (brunescent) or black (cataracta nigra). Ref: Eye pathology : An Atlas and text p.110.
Urochrome
Copper
Iron
Silver
Lens