What white sauce best compliments ravioli stuffed with mozzarella Swiss ricotta and parmesan cheesesand grilled white meat chicken?

It sounds like you're going for an entirely white dish. You could melt some butter in a pan, let it brown lightly, add a little chopped sage, let the sage toast and then toss the cooked ravioli in the butter. Or you could make a bechamel sauce (butter, flour, milk, a little nutmeg, and salt to taste). I wouldn't add cheese to the sauce since you have all the cheese you need in the ravioli. You could also serve the ravioli en brodo. That means in broth. A light chicken broth seasoned with some thyme or sage would be delicious.