Brazilian Cold Bean Salad

I encountered a delicious bean salad at an "a kilo" restaurant in Brazil.  You make it as follows:

1. cook great northern beans with a little salt, olive oil and garlic.  Drain afterwards
2. put in a large container and add some more olive oil and mix to lightly coat the beans
3. add chip chopped green and red bell peppers and onion
4. add some sort of acid.  I like to use lime juice but you can also use vinegar.  Add and mix a bit at a time until it suits your taste.