[iOS]: 如何改变MBProgressHud的背景方框的颜色

in MBProgressHud.m file，find 

CGContextSetGrayFillColor(context, 0.0f, self.opacity);

comment it and then add following line to set transparent bg color

CGContextSetFillColorWithColor(context, [UIColor clearColor].CGColor);

to set bg color as blue, use

CGContextSetFillColorWithColor(context, [UIColor blueColor].CGColor);

if you want to set opacity, refer to http://alwawee.com/wordpress/2012/06/30/change-mbprogresshud-color/