Place a saucepan over medium heat, add the oil and cook the ground/powdered cumin, turmeric powder, ground/powdered coriander, cayenne/red chili powder, whole spice powder, and sweet paprika.
Stir occasionally until spices are aromatic, this should take about 2-3 minutes. Set aside and allow cooling completely.
Whisk the Greek yogurt/hung curd to ensure there are no lumps. Add the spice-oil mixture to the yogurt and mix well.
Add the lemon juice, food coloring, garlic, ginger, and salt, and whisk until well incorporated.
Place the chicken legs on a cutting board and use a sharp knife to cut bone-deep slashes on the thigh/leg pieces.
Create the slashes on 4-5 places on each chicken piece, while being careful that you do not separate the chicken from the bone. Only create 2-3 deep cuts if you are using separated thighs and drumsticks.
Submerge the chicken in the yogurt-spice mixture and coat the chicken thoroughly in the marinade, ensuring there is plenty of the marinade between the slashes of the chicken. Cover the bowl, chill, and allow marinating for at least an hour. (see tips)
Prepare your griller by heating one side of it over direct heat; make sure it is quite hot. Do not place the other side over direct heat; let it be cooler. (see tips)
Soak a paper towel in a bit of oil or use a heat-proof brush dipped in oil to wipe/brush over the grill gates so that the chicken does not stick to the grill.
After one side of the grill is hot enough, take the chicken out and shake off the extra marinade from each chicken piece, the chicken should be well coated but not viscous-like.
Place chicken pieces over the hot side of the grill and cover for 2-3 minutes, without moving the chicken.
Ensure that the chicken is well charred on both sides after 2-3 minutes turn the chicken piece, so it gets the same color and texture on all sides.
After chicken is colored, transfer the chicken to the cooler side and allow cooking for at least 20-40 minutes, the cooking time would depend on how hot the grill is and the size of the chicken (see tips).
Optional: Heat a pan over medium-low heat and transfer the chicken to the pan after it is heated.
Place a piece of coal over a piece of aluminum foil and add the butter on top of the coal, smoke will emit so make sure you cover the pan so the smoke is trapped and the chicken develops a smoked flavor.
Rest the chicken for a few minutes before serving. Squeeze lemon juice on top and serve with naan or rice. Enjoy!