Custom view sometimes appears with wrong background color

I have a custom 'Dot' view that is a circle with a border and background color, similar to the dots in the upper-left hand corner of iOS 7+ that show signal strength.

A dot can either be filled or not filled.

Filled dot:

Not filled dot:

The problem: 20-30% of the time I launch the app, non-filled dots appear with a yellow background, even though white is explicitly specified.

Here is the code in drawRect:

- (void)drawRect:(CGRect)rect
{
    CGRect borderRect = CGRectInset(rect, 3, 3);
    CGContextRef ctx = UIGraphicsGetCurrentContext();
    if (self.filled) {
        CGContextSetFillColor(ctx, CGColorGetComponents([self.color CGColor]));
    } else {
        CGContextSetFillColor(ctx, CGColorGetComponents([[UIColor whiteColor] CGColor]));
    }
    CGContextSetStrokeColor(ctx, CGColorGetComponents([self.color CGColor]));
    CGFloat lineWidth = rect.size.height/10;
    if (lineWidth < 1) {
        lineWidth = 1.0;
    }
    CGContextSetLineWidth(ctx, lineWidth);
    CGContextFillEllipseInRect(ctx, borderRect);
    CGContextStrokeEllipseInRect(ctx, borderRect);
    CGContextFillPath(ctx);
}

self.color is never being set to yellow. Only the blue color you see as a border.

What could be causing these to sometimes appear yellow?