Lesbian roles and hair color

In 'Six Feet Under', Edie is a blonde established lesbian who straight red-headed Claire becomes drawn to for a while before deciding that she's not attracted to women in that way.

In 'Show Me Love' (Swedish film) Agnes, who is dark-haired, is the more obvious lesbian - but Elin, who is blonde, is the one who goes after her initially and really pushes the relationship along.

In 'Girl, Interrupted' Angelina Jolie's character is blonde and seductive, and it's suggested that she may be at least sexually ambiguous, though she isn't explicitly defined as a lesbian. Winona Ryder's dark-haired character, who otherwise seems straight, is very drawn to her. (Admittedly, WR is the one to instigate a kiss).

In 'If These Walls Could Talk 2', Chloe Sevigny's character is blonde (and butch), and she sort of seduces Michelle Williams' brunette character.... although MW already identified as a lesbian. But she is femme.

In 'Calamity Jane' (admittedly this isn't explicitly a lesbian movie), Doris Day's character is blonde and butch, and the female character she becomes friends with is femme and brunette

In 'The O.C', Olivia Wilde's blonde character is the established bisexual, whom otherwise straight and brown-haired Marissa is drawn to

In 'Sugar Rush', lesbian Kim is red-headed and straight/bi-curious Sugar (who has a few kisses with her) is brunette and biracial.

So I think there are probably examples on both sides.

ETA: Oh, and in 'The Hunger', Susan Sarandon's red-haired character is seduced by Catherine Deneuve's blonde character.

I think this image of the blond and innocent woman occured even before Nazi-Germany.

Just think about film and literature before 1933. Or think about literature for children back in 1850-1900; the heroine was most likely to be blond and innocent.