If the world was suddenly devoid of color (which I take to mean black and white of varying tints and shades) I would choose the sun to stay the same. In my mind that would make
The sun could play its rays across the landscape in golden hues (even if yellow isn’t my favorite color) during the day. It would be interesting to watch how the sun rays would play patterns with the clouds on the land.
Sunrise and sunset would bloom in their regular rainbow of colors. There would be a time of freedom (no work, school, or event planed (unless they planned for the free time)), maybe and hour, at sunrise and sunset to celebrate and watch the rainbow hues. The moon, which reflects the sun, would appear mostly the same.