From the site:
“THE ROUNDEL, or the diamond-shaped signs at railway stations mentioning its name, may seem like a humble identity marker for railway stations, but it has over the years seen changes, from its design, the number of languages in which it identifies stations to the recent changes to its shape. At its core, however, the roundel, like several other railway features, owes its design to the British, who laid the foundation of the present-day local railway lines.
Talking about the history of the roundel in his book, Halt Station India, railway historian Rajendra Aklekar says the signage, also termed “bulls eye”, has its origins in London. He says in 1908, the Underground Electric Railways Company of London used a winged, spoked wheel for its stations’ name boards and “fashioned a bright red circle with a blue bar across”.