All people used to wear purple in the past. 

Organisms years ago were green not purple.

In the Phoenician era, people could buy purple dye in the city of Tyre.

Ordinary people were allowed to wear purple in the 16th century. 

Purple colour was discovered in 1856 by William Henry.

William Henry Perkin discovered the colour purple by accident.

The purple dye became cheap when William Henry Perkin started his own company