Green with Envy

Why can't my pesto stay green like Costco bananas?  I am not complaining about the taste, it's delicious, but it looks like goose turds.  This batch is particularly dark, probably because I used a mix of purple and green basil.  

Is it because I used walnuts instead of pine nuts?  Did my basil that I raised from seed turn on me because I refused to pay $23 for a pound and a half of pine nuts at Costco? When they realize they are not mixed in with pignoli do they say, "Dude, it's walnuts again, blend in!" and go brown like a chameleon does when it's stressed out?  No matter, it will still do nicely with the tomatoes.

Pesto

a mess of basil leaves--about 3 cups worth

1/2 cup grated parmesan

salt and freshly ground pepper

2 small cloves garlic

1 cup walnuts

extra virgin olive oil

Combine all in food processor and puree til finely ground, then add olive oil with machine running until it loosens up into a saucy consistency.  Adjust seasonings.  Don't be afraid to add more salt--parmesan is salty but some more so than others.  I tend to go light on the garlic so it doesn't overpower things.  Makes about a cup.  If yours is still green at this point you can put in jar and cover with a thin layer of olive oil--should help it stay green.