The first evidence we have of purple or red shoes used for kings is more than 3000 years old.
Etruscans (an ancient Italian population) used red shoes for their kings[1], albeit its uncertain whether they could be purple which is more likely. This habit then moved to the roman kings and later the Roman emperors.
It is uncertain when it went from purple to red, but it's likely a practical reason: when going outside you don't wear slippers but leather boots, which were very easy to get in a red color, purple? Not really. You can easily find purple used anywhere in clothing, but not shoes.
And who else claims (or claimed) to be the heir of the Roman empire other than the Pope?
The emperor of byzanthium [2], notice how he's the only one depicted with red/purple shoes.
The German emperor [3].
The Tsars [4] (Tsar word comes from Caesar, same as Kaiser) too claimed the inheritance of the Byzantine (and thus Roman) empires after the Ottomans took the city.
The first evidence we have of purple or red shoes used for kings is more than 3000 years old.
Etruscans (an ancient Italian population) used red shoes for their kings[1], albeit its uncertain whether they could be purple which is more likely. This habit then moved to the roman kings and later the Roman emperors.
It is uncertain when it went from purple to red, but it's likely a practical reason: when going outside you don't wear slippers but leather boots, which were very easy to get in a red color, purple? Not really. You can easily find purple used anywhere in clothing, but not shoes.
And who else claims (or claimed) to be the heir of the Roman empire other than the Pope?
The emperor of byzanthium [2], notice how he's the only one depicted with red/purple shoes.
The German emperor [3].
The Tsars [4] (Tsar word comes from Caesar, same as Kaiser) too claimed the inheritance of the Byzantine (and thus Roman) empires after the Ottomans took the city.
[1] https://www.pope2you.net/wp-content/uploads/2019/06/Etruscan...
[2] https://www.thoughtco.com/thmb/QytBnfnDoP8aDE-rm3eYGbTYCpk=/...
[3] https://www.ancient-origins.net/sites/default/files/field/im...
[4] https://www.mediastorehouse.com.au/p/731/tsar-boot-antiquiti...