Combine hoisin sauce, soy sauce, wine, honey, sugar, garlic, colouring (if using) and spice powder in a shallow bowl. Whisk well to combine. Pour half of the sauce into a jug and reserve for later. Add the pork into the bowl with the remaining sauce. Rotate to cover completely and marinate in the refrigerator for 1-3 hours, or cover and refrigerate overnight for best results.
After marinading, preheat oven to grill/broil settings on medium heat (176°C | 350°F). Drain pork and discard the marinade. Line a baking pan with baking/parchment paper or aluminium foil. Place pork onto pan and grill/broil for 30 minutes on one side, basting two or three times with the reserved marinade. Rotate with tongs and baste again with the marinade twice again while grilling/broiling.
Remove from oven and allow to cool.
If you like additional glaze, combine all of the (extra) glaze ingredients into a small saucepan. Bring to a boil; reduce heat and allow to simmer for about 5-8 minutes until the sauce has thickened (keep your eye on it as it can burn easily if the heat is too high). Remove from heat and allow to cool slightly.
Cut pork into thick slices to serve. Serve over steamed rice and/or vegetables with the extra glaze.