Dyeing with lichen does not need a mordant. Lichen dyes are part of the group of early Anglo Saxon dyes that were used on wool for embroidery and other small embellishing projects. It was used in some parts of the world to immitate Tyrian Purple from mollusks which was an extremely expensive dye reserved only for the very rich.
 
This lichen will give peach to deep orange when boiled and  red, blue or purple depending on the Ph level when using the ammonia steep method.
Soak a handful of lichen in stale urine or in a solution of two parts water to one part of ammonia in a glass jar with a lid.
Air and shake the solution every day.
Lichen dyes can take several weeks for the color to develop so patience is a virtue
 
When the solution has a rich hue, strain off the liquid into a dye pot and add the fibres to be dyed, and add more water to fully cover. Heat the solution gently to just below a simmer and hold on temperature for about 30 minutes. Allow the fibres to cool down the solution overnight. Remove the fibres, squeeze the excess liquid back into the pot and re-use the solution until it is exhausted.
Using an acidic modifier post dyeing will make the fibers redder. 5% alkaline modifier, like soda ash or potash will turn the firbers purple to even blue.
 
Wildcrafted from Macedonia from the forest floor. 
Other dyes in this category are Oak Moss Lichen and Icelandic Moss