Lichens

OK, I know little about lichens but have some questions. These yellow and white ones always seem to be together on Coastal rocks with the fresher looking yellow, some almost orange, growing on the white which appears old and washed out. Is it perhaps a single species which start out orange and fades through yellow to grey/white as it ages. I think the bright sun made the grey look white in the sun. Knowing that many lichens can only be determined for certain by specialised testing and microscopic analysis I have not attempted to find anything definite except to say that Ochrolechia parella and Xanthoria parientina look superficially similar and are found on coastal rocks in this area, as of course, are several other species.