We’ve always associated buses of the Brihanmumbai Electricity Supply and Transport (BEST) undertaking with red but did you know that there was a point when that was not the case? Over the years, we’ve seen some exceptions to the rule, such as the vestibule fleet that was yellow in colour, much like the current Tejaswini fleet for women. Similarly, the JCBL Cerita (erroneously referred to as Kinglong) was purple in colour (hence I referred to them as Purple Faeries) and the Tata Starbus Hybrid fleet was silver in colour. Of the six Volvo buses in its fleet, a few were orange while the rest were red, although only the front of the bus reflected this, given that advertising covered the sides as part of the acquisition deal. However, barring these, the fleet has pretty much been red. The same applied to trams too. However, there was one period when the buses were painted a different colour.
India was an active participant in both World War I and World War II as a part of the British Empire. As a result, Indian cities, especially the larger ones were at high risk of being attacked by the enemies. While electricity was yet to reach all parts of the city, public areas were often illuminated and buses and trams, being a bright-red colour were at constant risk of being targeted.

Thanks to Shubham Padave, Yatin Pimpale for the information. Thanks to BEST for the image.
Featured Image: An AI-generated rendition of a BEST bus in military olive green; generated using Dall-E 3 on Bing.