Bring a large pot of water to a boil.
Prepare an ice water bath in a large bowl.
Heavily season water with kosher salt (at least a tablespoon). Drop 1 pound green beans into boiling water and cook until crisp-tender and vibrant in color, about 3 minutes.
Using a slotted spoon or spider, immediately transfer green beans to ice water bath and let cool completely.
Whisk together 2 tablespoons oil, 2 tablespoons vinegar, 1 tablespoon lemon juice, 1 tablespoon chives, 2 teaspoons mustard, and 1 teaspoon honey for the vinaigrette; season with ½ teaspoon salt and ½ teaspoon pepper.
Drain beans and dry well (either in salad spinner or with paper towels).
Toss green beans and 1 cup grapes with vinaigrette; season to taste with additional salt and pepper. Transfer salad to a serving bowl or platter and top with 1 cubed avocado and 2 ounces crumbled blue cheese.