Camera colour isn't quite true - lichen was a pale sulphur yellow. It occured on certain bricks on the church, making them appear very yellow!
No identification made yet.
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Hi, take a look at http://www.lichens.lastdragon.org/Psilolechia_lucida.html
A selection of photographs, some from churchyards, that might fit your description.
Your left-hand photograph is so green that it looks like a Lepraria (& one species, L. ecorticata, not yet up on my site, is not unlike Psilolechia lucida), but I take your word for it that the colour is wrong. Digital cameras are often very poor at accurately recording lichen colours, and one of the photographic magazines reveals alarming differences in colour perception between cameras, especially for yellow-green, in its reviews.
Many thanks Alan - the colour in my photo of the church is much more accurate and very similar to yours.
The age and stile of the building makes me think that some kind of chemical that has been added to some of the bricks for cosmetic effect is doing it. These might oxidize in order to produce the yellow look to contrast with the black bricks. Cameras do mess with the colors of chemical salts if there is a miss match between the ones being photographed and the ones the chip or film is made from. Lichens also concentrate mineral salts inside themselves and that is consistent with what the magazines have said.
Lat/Lng: 51.04134, -0.60989
OS grid ref: SU975278