Sauté bell peppers, yellow onion, and garlic in 2 Tbsp. hot oil over medium-high heat 8 to 10 minutes or until tender. Stir in mustard and next 4 ingredients. Add breadcrumbs, and sauté 1 minute. Transfer mixture to a large bowl. Cool 15 minutes.
Fold eggs into breadcrumb mixture until blended. Gently stir in crabmeat and green onions. Shape into 12 (3-inch) crab cakes (about 1/3 cup each). Cover and chill 30 to 40 minutes.
Melt 1 Tbsp. butter with 2 Tbsp. oil in a large nonstick skillet over medium heat. Add 4 crab cakes to skillet; cook 3 to 4 minutes on each side or until browned. Remove from skillet, and keep warm in a 200° oven. Repeat procedure with remaining oil, butter, and crab cakes, wiping skillet clean after each batch. Serve with Lemon Butter.