In 1968 I joined the publishers William Heinemann as their art director. I inherited many existing literary series including the LOBE Classical Library with their traditional wrappers (below).
They were first published 1912 and have been continuously in print, now under Harvard Press, and still with their covers unchanged, green for Greek and red for Latin.
Back in 1968, I found them rather dull looking and wanted to change them but wasn't allowed to.
50 years on I find them rather comforting and completely appropriate.