Answer:
Yellow.
Explanation:
An object that reflects all the incidents colors of light will surely reflect off the color yellow, and when the reflected ray hits our eyes, we will perceive the object as yellow. The object that reflects off all colors appears to us as white. So if you want to make sure, then just shine yellow light on a white fabric and see what happens!
What you will observe of course is a yellow fabric. Similarly, if you shine red light onto the fabric, it will appear red, and so on for all colors.
