There are a vast number of plants from which you can obtain dye. I have always presumed that most of them would produce decidedly earthy colours compared to the bright synthetic dyes we take for granted in modern life. I could not have been more wrong.
Please note that not all lichens produce a dye so please do your research before you forage for them. Many grow exceptionally slowly, so it is essential to gather responsibly to avoid damaging colonies. We currently have two lichen dye projects on the go.