The only difference between green olives and black olives is how long they ripen on the tree. The green ones are earlier…if they are there long enough they turn darker. The olives taste incredibly bitter, and make you pucker – kind of a combination of that very unripe-banana feeling mixed with the involuntary pucker you make when you eat a lemon. Salt leaches out the bitterness. People cure olives now with lye but originally in the mediterranean they were cured with salt, an abundant resource near the ocean. I cure my own olives here in California, thanks to some help I got on fluther from a fellow flutherite who lived in Portugal and helped me out with a recipe. search keyword “Olives” on fluther and you’ll find it. If you ever are in california in October, you can find fresh olives in the farmer’s markets.