Explanation:

Corona Discharge:
Corona discharge is a phenomenon that occurs when a high voltage is applied to a conductor with a very sharp point or edge, creating a faint glow or halo of light around the conductor. This glow is typically bluish in color.

Reason for Bluish Color:
- The bluish color of corona discharge is due to the excitation of nitrogen molecules in the air by the high voltage electric field.
- Nitrogen is the most abundant gas in the atmosphere and is responsible for producing the characteristic bluish glow.

Other Colors:
- While the typical color of corona discharge is bluish, it can also appear as purple or white depending on the composition of the surrounding gases and the intensity of the electric field.
- However, in general, corona discharge is most commonly observed as a bluish glow.

Importance of Color:
- The color of corona discharge can be used by engineers and technicians to diagnose problems in high voltage systems.
- By observing the color and intensity of the corona discharge, they can determine if there are any issues such as excessive electrical stress, insulation breakdown, or contamination.
In conclusion, corona discharge is generally bluish in color due to the excitation of nitrogen molecules in the air by the high voltage electric field. This bluish glow is a key characteristic of corona discharge and can provide valuable information about the condition of high voltage systems.