[{"_id":"Colorcode_1","Combination":[{"color":[{"mixture":["Red","Green"]}],"code":"Maroon"},{"color":[{"mixture":["Yellow","Green"]}],"code":"Light Green"}]}]

db.collection.update({"Combination.code":"Maroon"},{"$addToSet":{"Combination.$[x].color.$[y].mixture":"Blue"}},{arrayFilters:[{"x.code":"Maroon"},{"y.mixture":{$exists:true}}]})