Iran was always called Iran inside the country - it was only called Persia by the West. The Greeks called Iranians - "Persians", but those within the country or the former empire called their country Iran - which translates to Land of the Aryans.
The lighter featured populace are not mixed - they are a part of various regions in Iran. The only darker featured Iranians are on the border with Iraq [consisting of the 2% Arab populace] and with Pakistan [where the Baluchi minority lives].
No it was not always called Iran. Listen,
Iraq Iran India Pakistan Afghanistan Armenia are all derivatives and various translations from the word "Aryan" since Sanskrit is a language that comes from India and is thus an Aryan language. Persia changed to "Iran" as its national title right around the 1960's only because it had an arrogant ego trip to supposedly show that they are "the lords" as the Ayatollah once tried.
The lighter ones amongst Persians today are the mixes because for years Persians have pillaged lighter people and thus their cultures clashed and they mixed. They mixed with cultures whom are White and have those blonde hair and blue eyed features:
1) Armenians
2) Greeks
3) Romans etc.
They do have an Aryan BRANCH but alas they are not the source of Aryans. And also, the facts remain: that blonde red hair blue green eyed feature is a genetic mutation found only among the WHITE race. That is common only amongst White people because it comes from the climate just as other genetic mutations are all common amongst other races. There is no way in hell that Germans--who come from Germany north of the equator where they barely see sun-- could have been naturally dark skinned and haired. Colder regions as logic and anthropology shows they have little sunlight thus preventing them from getting natural dark skin. They are not prone to getting dark skin because they have adapted to their climate.