Mi sono innamorato di Marina Una ragazza mora ma carina .... WTF???

I loved the movie, but seriously, I don't get it. Who he was singing to?
This song says that Marina was brunette, girl with a dark hair.
Helena clearly has blonde hair in this movie.
And that is so freaking confusing. First, her name was Helena, second,
she had blond hair. Third, he looks at her, he's in love with her, and
in the whole movie, it looks that song came out of nowhere, and was not
for her. I can hardly believe he didn't know her name for so long, but okay, let's let that slide - he looked at the wall and saw name that inspired him, but what in the world inspired him to write a song about a brunette, that is, I mean, why in the world wasn't actress at least with matching song color of the hair????
Oh, the humanity...