Final answer:
The photosphere gives the Sun its color, but during a total solar eclipse, the red color is most notably perceived from the chromosphere, which is immediately above the photosphere.
Step-by-step explanation:
The layer that gives the Sun its color is the photosphere. However, it is the chromosphere, the region of the Sun's atmosphere that lies immediately above the photosphere, that significantly contributes to the Sun's color during a total solar eclipse, revealing a reddish color. Observations made during such eclipses show that the chromosphere is about 2000 to 3000 kilometers thick and emits bright emission lines, especially a striking red line from hydrogen, which dominates the Sun's composition. While the corona is the outer atmosphere of the Sun and is visible with X-rays, it is not the source of the Sun's overall color.