Richard Short - artist - died in 1916.
Richard Short - artist - was born in 1841.
Richard King - artist - died in 1974.
Richard Coyne - artist - died in 1990.
Richard Cook - artist - died in 1857.
Richard Allen - abstract artist - died in 1999.
He died, "from an extensive disease of the lungs".
See the link for 10 Richard Longs, hopefully one of them is the one you are asking about. If it is the artist Richard Long, he is still very much alive.
Richard Phillips - artist - was born in 1962.
Richard Grayson - artist - was born in 1958.
Richard Whitney - artist - was born in 1946.
Richard King - artist - was born in 1907.
Richard Coyne - artist - was born in 1926.