The chromosphere is a layer of the Sun's atmosphere that's usually hidden by the bright photosphere. It becomes visible during a total solar eclipse.

Here's how the color changes during totality:

* Start of totality: The chromosphere appears bright red due to the hydrogen gas it contains. This red color is caused by the emission of light at the H-alpha wavelength.

* End of totality: As the Moon moves away, the chromosphere fades quickly and becomes less visible again.

So, the chromosphere is red at the start of totality, but it fades as the eclipse progresses.