Personally, I've never tried to paint a leather look on louvers. I'm sure it is possible and would look nice. My biggest concern is getting a primer to stick so your paint won't peel.
A good primer to use is <a href="//www.painters-toys.com/xim-plastic-and-vinyl-primer.html" target="_blank">XIM Plastic and Vinyl Primer</a>. It does stick to most plastics.