Possible Clues:

• A brown pigment
• Pigment not new in aggregate
• Dark to reddish brown
• For the unaspirated, the river becomes brown
• Crayola color
• Dark brown coloring matter
• The earth is brown for the unaspirated in the North of England
• Brown earthy substance used as pigment
• Might Brown, being unaspirated, place this in Yorkshire?
• Natural pigment from estuary identified by Cockney?