Fresh garlic turning green in slow cooker?

I am making Slow Cooker Butter Garlic Chicken form the New York Times cooking app and the fresh chopped garlic is turning green an hour and a half in to the four hour cook time. Should I be worried?

This is the recipe, minus parsley that I didn’t have:
1½ to 2 pounds boneless, skinless chicken thighs

2 (15-ounce) cans cannellini beans, rinsed (I used one can)

4 tablespoons unsalted butter, cut into chunks

8 large garlic cloves, smashed and chopped

1 shallot, minced

1 lemon, juiced 

Combine the chicken, beans, butter, garlic, parsley, shallot, lemon juice, 2 teaspoons salt and several generous grinds of pepper in a 6- to 8-quart slow cooker. Cook on low until the chicken is tender and the flavors have mellowed, about 4 hours.