In a large bowl, combine soy sauce, hoisin sauce, honey, rice vinegar, sesame oil, five-spice powder, minced garlic, grated ginger, vegetable oil, and red food coloring if using. Whisk until well combined.
Add the chicken thighs to the marinade, ensuring they are fully coated. Cover the bowl with plastic wrap and refrigerate for at least 2 hours, preferably overnight for maximum flavor.
Preheat your grill or oven to 400°F. If using a grill, lightly oil the grates.
Remove the chicken from the marinade, allowing excess marinade to drip off. Reserve the marinade for basting.
Grill or bake the chicken for about 25-30 minutes, turning occasionally and basting with the reserved marinade, until the chicken is cooked through and has a nice caramelized exterior. The internal temperature should reach 165°F.
Once cooked, remove the chicken from the grill or oven and let it rest for 5 minutes before slicing.
Serve the sliced chicken garnished with green onions.