If you are just trying to fill the smaller oval with a white colour, change your fillColor2 code to this:
UIColor *fillColor2 = [UIColor colorWithRed:1.0 green:1.0 blue:1.0 alpha:1.0];
or this:
UIColor *fillColor2 = [UIColor whiteColor];
The smaller circle is showing up black because filling red, green, and blue values with 0 results in black.