There was a film made in 1968 (http://www.imdb.com/title/tt0063683/), I don't think it's been done since then. However, a French director just made a biopic about Leduc which is currently doing the rounds on the festival circuit, maybe you're thinking of that. I think it's called Violette.

That's probably it then. There is a recent film with an extended lesbian sex scene that has everyone riled up but I can't remember the title.

Ah no that's Blue is the Warmest Colour, amazing film! I wrote about it quite a lot here).