Ali Shariati was one of the intellectual godfathers of the Revolution. He actually did try to merge Islam and Marxism, the terrorist group MeK is a legacy of it.
MeK has a long history in Iran, definitely before Ali Shariati. MeK over the decades also has reinvented itself a few times for how it *positions & sells* its ideology to people.
Both MeK and Ali Shariati are/were 100% followers of Islam First & Foremost; then tried to incorporate communist elements of *history & politics* with it (mostly that of Lenin). BUT, both subscribing to a ‘revolutionary Islamic approach’.
Ali Shariati (a hardcore Islamist who died in 1977) was of the belief that there is a “Red Islam” (in addition to black and green Islam - yes, colour-coded & mean different things). The colour meaning and symbolism also varies slightly between shi’ites & sunnis.
“Red Islam” term, however, never referred to “communism” (and was Not used in Soviet context); it referred to shia imams such as Hossein and Ali (pure shia 12ers Islam), who were revolutionaries in their time, fighting for & spreading their brand of Islam by blood (red).
That said, there are many mullahs/ayatollahs, including those within the current regime, who are either Leftist-Islamists (like Khamenei, the present Supreme Leader, who actually studied in the USSR), AND, there are Right-wing Islamists (such as Ahmadi-Nejad). Needless to say, both (factions) are atrocious & no good.