From the National Trust guidebook:
Charles Paget Wade (1883-1956), the last owner
of Snowshill Manor, who purchased it in 1919, said that
artificial colour must only be used with care: "Never paint a
'nature' green -- turquoise is the most satisfactory colour, a foil to
the grass and foliage." In fact, his own creation, Wade blue,
is subtly different from turquoise.