Collect white, soft plastic tins to make your guitar knobs. Wash and then dry them to remove any grease and dirt. Cut them into small pieces in order to melt them easily. Cut enough to make 4 guitar knobs. Design the shape and color you want on paper. Make a fire place outdoors. Use two empty medium sized metal containers to heat the plastic pieces till they melt. Divide the melted plastic pieces into two and put each half into the heated tins. Take care not to burn or put any liquid in it.
Stir carefully taking care not to make any body contact with it. Don't allow the molten plastic to bubble. Once molten, remove the two tins from the fire and let them cool slightly. Add green dye to one half of the molten plastic and the orange dye to the other half while still malleable.Work them very fast to mix in the dyes completely.
Transfer the molten plastics to a marble slab when the plastics starts to cool. Mold the plastics into the shape of a golf club head. Use alternating colors to form a rainbow pattern and shape one side into a golf club head of 2 inches across and an inch stem, smooth out any lumps when the plastics are still malleable, making sure you size them equally. Insert the nuts at the bottom center of each stem and push them in completely to give a clearance of 1mm and let them cool. The nuts save you the trouble of drilling and making threads into the stems. Work very fast when they are still malleable.
Trim the flat bottom surface of the stems to make them flat and smooth. Use an engraving tool to make designs on the top of the knobs, include a logo or a suitable name and mark with black color. The top of the knobs should resemble golf club heads. Rub out any loose black color to make the engravings look simple and neat.
Screw the nuts into the jutting bolts from the guitar. Turn the knobs clockwise to tighten them. Make sure you adjust the guitar knobs and test the compatibility of the knobs by turning them to the extreme ends and trying to force them on. When they don't move at the extreme ends then the knobs are compact. You now have rainbow designed plastic guitar knobs with strong metal threads to secure when you fit them into threaded bolts.