Final answer:
Copper (II) sulfate is the element that is most likely to show a vivid color in a solution when dissolved in water.
Step-by-step explanation:
The element that is most likely to show a vivid color when dissolved in water is copper (II) sulfate. Transition metal compounds, such as copper (II) sulfate, exhibit a wide variety of bright colors when dissolved in water due to the absorption of light by their d-orbitals. Copper (II) sulfate, in particular, produces a blue-green solution.