Here's why:

* Flame Tests: Flame tests are a common way to identify elements based on the color of light they emit when heated.

* Excited Electrons: When copper chloride is heated, the electrons in the copper atoms become excited and jump to higher energy levels.

* Returning to Ground State: As the electrons return to their ground state, they release energy in the form of light. This light is in the blue-green part of the visible spectrum.

Red flames are typically associated with other elements, such as strontium (bright red) or lithium (crimson red).