Another way to prevent the pesto from turning brown is by blanching the basil leaves in boiling water and refreshing it in ice water immediatly after, press out as much water as you can without squeezing the juice out of the leaves. Then blend everything together.
Other variants include, wallnut and rocket pesto, sundried tomato and chives, chives and pinenuts(a touch more black pepper and salt)... These are only what I have made at the establishments where I have worked. Pestos can be used in so many places with so many combinations.
Delta!