Food coloring will not disperse in vegetable oil, or any other kind of oil, and therefore cannot be used to color it. However, a fun experiment exists to combine food coloring and oil as a makeshift lava lamp.
This experiment requires a plastic bottle, vegetable oil, water, food coloring and an effervescing antacid tablet.
Step 1: Combine oil and water
Start with a plastic bottle and fill it about 2 inches from the base with water, then fill most of the bottle with oil.
Step 2: Add color
Add a few drops of food coloring. These will not disperse until reaching the water at the bottom of the bottle.
Step 3: Introduce the antacid tablet
Drop the effervescing antacid tablet into the bottle and watch it descend to the water. There, as it dissolves, it will release bubbles of colored water into the vegetable oil. Shining a flashlight through the bottle can enhance the lava lamp effect.