While you are correct in that it is an exonym, it's not exactly what I, and I assume many others today, would think of when you say "colonial." The origin of the word dates back to thousands of years ago when no present government or society existed.

For those who would like to read a little more: https://en.wikipedia.org/wiki/Name_of_Iran

Absolutely its normally used to refer to the Persian "empires" which you know colonised other lands and where a lot larger that Iran is today.

from your link: "In the Western world, Persia (or one of its cognates) was historically the common name for Iran"

so I will stick to saying colonial as it accurately points to the western world as opposed to Africa or Asia for example

I don't disagree about the name that should be used, as I said. I just think calling it colonial needs a little more context for people who would not unreasonably assume it's something more similar to Western colonialism of India or something.

On that note, "India"/Hindustan/Hindu/etc. are somewhat similarly colonial-rooted names, ironically popularized by the Iranians.

"western colonialism" is redundant. "colonialism" will suffice :)

It's out of date, but that's OK when talking historically. And it was no more colonial than saying "Germany" instead of "Deutschland". Personally I prefer the term "Iran" even for historical usage because it is both older and (usually) more accurate.

But "Persian" is not something that foreigners imposed. It was originally the name of a particular Iranian nation that took over the empire thousands and of years ago. Their name then stuck around in some contexts long after that dynasty was gone, which is why the language is called "Farsi" (anglicised to "Persian").