Some scanners will put a color on a reflective CD.
And the color replacement tool can be used to make the disc look gray.
Use the color replacement tool
Set the color to white. It won't really make it white, it's more of a hue adjustment.
Place the cursor over the area to be adjusted. Then without releasing the mouse button, drag the circle all around the image.
To clean up dust and hair, use the inpaint brush
Click on the area to be fixed.
You can drag the mouse around to select larger or irregular shaped areas. A red mask will be shown for the area to be fixed.
Final result.