Cook the green lentils (rinsed and drained) according to package instructions. Halfway through, add the red lentils, stir to combine, and let both lentils finish cooking together in the same pot.
(Do this step while the lentils are cooking.) In a large pan, saute the diced onion and bell peppers in vegetable broth over medium heat until the onions are soft and translucent.
Add the minced garlic, chili powder, smoked paprika, tomato paste, and salt. Stir to combine and let the mixture cook for 2-3 minutes or until fragrant. You might need to add a splash of water if the mixture gets to dry and it's sticking to the pan.
Add the maple syrup, vegan Worcestershire, balsamic vinegar, ketchup, and water. Stir to combine and let it cook for 2-3 minutes so the flavors begin to meld together.
Add the cooked lentils to the pan, stir everything together, and reduce the heat to medium-low and let it cook for 15 minutes. Spoon the filling into vegan burger buns and enjoy!