I feed both cories and livebearers TetraDelica bloddworms, brine shrimps and daphnia for live food.
For veggies I usually feed the livebearers boiled peas or boiled sprouts, sometimes boiled spinach or chard, sometimes banana, apple or pear. I deshell the peas and mash them a bit, the sprouts and spinach/chard I chop very finely. The banana, apple or pear I scrape off a thin sliver with a knife and then chop/crush that. Actually, I only tried pear for the first time yesterday, but it was a success. Peas are the absolute favourites though; it's the only one, apart from pear, they've taken to straightaway; the other things I've had to try at least twice.
The cories tend to ignore any fruit or veg.