Fawn seems now to be called Beige

Nigger was what black labradors were named when I was young
 (though nigger-brown meant chestnut-coloured)
Puce is the colour of squashed fleas
Magenta was a battle celebrated by an early artificial dye
 and by a famous Paris boulevard
Reds are found beneath Louisiana beds
 and (with black) is the colour of Hell
Yellow were the bellies of eels and men of Lincolnshire
 who may have been unusually prone to jaundice
 (and is The Colour of Coyotes - another good title for a book)
Purplish are the acorns of men's cocks
 and many find it suitable for scarves and socks
 Red-Purple dye came once from boiling small Tyrrhenian molluscs
 now choked by microplastic
White is the colour of the Most Evolved Zincky-Flakey and Callow
 - and probably of God and Racism and fantastic Chance
Mauve is named after the flower and was also known as Mallow
Orange is the brazen shade of the monarchs of the Netherlands,
 is a town in France, and (as a fruit) lost its initial N in France
Blue meant sad (or beaten black and) way back in the 1300s
 A ship which lost its captain flew a blue flag

Brown was the mistress of a notorious German leader
Black (see also above) was an Irish Augustinian hag
 (Cailleach Dhubh) reputed to have been a witch
Grey is the polluted water in a ditch
 and the colour of money the minds of the rich
Green composed Aida