Ensure all grapes are completely dry after washing to prevent the dressing from becoming watery.
In a medium mixing bowl, beat the softened Neufchâtel cheese until smooth and free of lumps.
Whisk in the Greek yogurt, honey, and vanilla extract until the mixture reaches a uniform, creamy consistency.
Place the red and green grapes into a large serving bowl.
Fold the yogurt mixture into the grapes using a silicone spatula until every grape is thoroughly coated.
Sprinkle the chopped walnuts evenly over the top of the salad.
Cover and refrigerate for at least 30 minutes before serving to allow the dressing to set and flavors to integrate.