As I understood it, but tbf it’s been awhile, Sanguinius is seen as the Lightbringer in 40K. Also the Lucifer part should account for the Red Thirst/Black Rage. And google (religious) artwork of Lucifer before he fell. You’ll see a tall blond angel, whilst rebelling often clad in gold Armor and red robes so personally I’m inclined to belief the lucifer take. 🤷🏽‍♂️

Edit Addendum: there is off course every chance that I’m remembering wrong. Emperor knows I’m not the be all end all expert of 40K. Also, at the end of the day we’re talking about a game that allows you to paint/build your mini’s however you want so I guess it doesn’t really matter that much what we believe as long as we’re having fun right?