Gather and measure all ingredients; open and drain the canned kidney beans and chickpeas, rinse under cold water.
Trim the ends of the fresh green beans and cut them into 1–1½ inch pieces; if using canned green beans, drain and roughly chop.
Bring a pot of salted water to a boil and prepare an ice bath in a large bowl.
Blanch green beans in boiling water for 2–3 minutes until bright green and tender-crisp, then transfer immediately to the ice bath.
Drain the chilled green beans thoroughly.
Finely dice the red onion and red bell pepper; chop the parsley; if using garlic, mince it finely.
In a mixing bowl, whisk together olive oil, apple cider vinegar, Dijon mustard, honey, salt, pepper and optional crushed red pepper until emulsified.
Place rinsed kidney beans, chickpeas and blanched green beans in a large mixing bowl; add diced onion, bell pepper and parsley.
Pour the dressing over the beans and toss gently to coat, taking care not to mash the beans.
Taste and adjust seasoning with more salt, vinegar or honey as needed; let sit at room temperature for 15–30 minutes to meld flavors, then cover and refrigerate at least 1 hour before serving.