2. Put a small amount of grey acrylic paint onto a folded up paper towel.
3. Apply the paint very thinly to the inside of the lamp shade by dabbing and rubbing to create some darker spots and some lighter spots until you have peppered the entire internal surface with some degree of paint.
4. Allow to dry for 5-10 minutes.
5. Re-insert the bulb and observe the results.
If you use a Philips Hue or other colour changing bulb, try different shades of yellow, red and blue to create the full realistic effect.