In a medium bowl, add the Cheddar, mozzarella, yogurt, chives, salt and pepper, green and red peppers and jalapeno. Stir well to combine. Spread the mixture evenly among 4 slices of bread and top with a couple of slices of tomato. Top with the remaining slices of bread.
Spray a large nonstick saute pan over medium heat with nonstick spray. Place the 4 sandwiches in the pan and let cook until lightly browned, about 4 minutes. Flip the sandwiches and continue cooking until the cheese melts, another 4 minutes. Serve immediately.