There are a lot of different varieties of eggplant. Some are purple, some aubergine, some white, some mottled white/purple. That's just the way God made them!
Good way to cook them is to peel skin off, cut into fingers, dip into egg/milk wash, then in seasoned bread crumbs and fry. Instead of salt, sprinkle w/ grated parmesan while hot. Serve w/ marinara sauce for dipping.
Or make baba ghanoush, an eggplant dip nice for chips or pita bread dipping.
And eggplant parmesan is a classic. I like Mario Batali's recipe (on Food Network .com)