Gyalolechia allochroa

Gyalolechia allochroa is a species of saxicolous (rock-dwelling) crustose lichen in the family Teloschistaceae. It forms a thin, smooth crust on siliceous rocks in subtropical mountain regions and shows marked colour variation, occurring in both bright yellow and grey-white forms depending on light exposure. The lichen is characterised by abundant disc-like fruiting bodies with egg-yolk yellow rims and contains the pigments parietin and fragilin, which account for its distinctive colouration. It is known to occur only on three mountains in South Korea, where it was first discovered and described in 2011....read more on Wikipedia.