Penguin's colour-coded book series

Each book series was colour-coded by genre

Penguin Books were launched in the United Kingdom in 1935. Most of the early titles were paperbacks orange covers. Soon began publishing book series, the cover of each series being colour-coded to indicate the series to which the title belonged.

For example:
• Green for crime novels
• Cerise for travel and adventure
• Dark blue for biographies
• Red for drama
• Purple for essays
• Yellow was for miscellaneous titles, like crosswords
• Grey for world affairs

Penguin Books was not the first book publisher to use the colour coding for its series. Beginning in 1932 the German book publishing house, Albatross Verlag, used colour coding for each of the sub-series (green for travel, orange for fiction, etc.) in its book series, the Albatross Modern Continental Library.