Crottle

It was known and uſed as a dye-ſtuff in the Highlands of Scotland by the name of corkes or crottel, ſome hundred years ago.

Source: wiktionary

Not that crotal and white was as humdrum as a simple definition of it as ‘brown and white’ implies. Crotal was the grey lichen which, over hundreds of years, had grown over the moorland rocks particularly

Source: wiktionary

Parmelia omphalodes and P. saxitilis, the “crottles” used traditionally in Britain and Ireland, are sub-alpine lichens in North America.

Source: wiktionary

The older people, they knew all about the dyes, and we’d go and gather the crottles [a kind of moss used for dyeing woolens]. I don’t know what you call them here. They were round and you’d scrape them off a rock or stone.

Source: wiktionary