Illustrator Object won't let me change to color - only grayscale.

Hi,

I created some shapes in Illustrator and cut them apart using pathfinder and now i just want to change the inside of a shape from white to purple but it will only turn to shades of gray. I've cut and pasted into a new file where I've made other color objects but this particular object will only change to shades of gray. I'm so aggravated - what can I do?