There is no general rule as to how a capacitor should look. The capacitance value is usually marked, along with the maximum voltage rating. Some capacitors are marked with colour bands - these allow us to read the capacitance value. It should be noted that some capacitor designs have particular restrictions as to which way around they should be connected. Earlier we discussed water models of resistors and batteries, as well as water models of simple circuits.
Capacitors also have their water models, although somewhat more involved.
A water-filled cylinder with a movable piston works in analogy to a capacitor. The piston is attached to one side of a cylinder with a spring. In operation, no water passes around the piston. As water flows, it displaces the piston, and compresses or stretches the spring. Externally applied changes of water pressure on one side are instantaneously passed through to the other side.