In a large bowl, combine soy sauce, hoisin sauce, honey, rice vinegar, Chinese five-spice powder, sesame oil, garlic, ginger, and red food coloring (if using). Whisk until well blended.
Add the chicken thighs to the marinade, ensuring they are fully coated. Cover and refrigerate for at least 4 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, reserving the marinade for later.
Grill the chicken for about 6-8 minutes per side, or until the internal temperature reaches 165°F. If baking, place the chicken on a lined baking sheet and bake for 25-30 minutes, basting with the reserved marinade halfway through.
Once cooked, let the chicken rest for 5 minutes before slicing.
Garnish with sesame seeds and sliced green onions before serving.