Cook lasagna in water 10 to 15 minutes and drain. In a stainless baking pan, put olive oil in first. Add one layer of lasagna, add ricotta and mozzarella, then green squash. Add another layer of lasagna, both cheeses and yellow squash. Repeat until ingredients are finished. Top with mozzarella and bake about 15 to 20 minutes at 350 degrees. Top with spaghetti sauce if desired.