How to draw a transparent UIToolbar or UINavigationBar in iOS7

TransparentBar.m

/*
Setting translucent to YES on the navigation bar does the trick, due to a behavior discussed in the UINavigationBar documentation. I'll report here the relevant fragment:

If you set this property to YES on a navigation bar with an opaque custom background image, the navigation bar will apply a system opacity less than 1.0 to the image.
*/

// Transparent UINavigationBar
[self.navigationBar setBackgroundImage:[UIImage new] forBarMetrics:UIBarMetricsDefault];
self.navigationBar.shadowImage = [UIImage new];
self.navigationBar.translucent = YES;

// Transparent UIToolbar
[self.toolbar setBackgroundImage:[UIImage new] forToolbarPosition:UIBarPositionAny barMetrics:UIBarMetricsDefault];
[self.toolbar setShadowImage:[UIImage new] forToolbarPosition:UIToolbarPositionAny];

What if i like to have some transparent color? like #7919ca with opacity 80%? this method only work when u need to have a clearColor

You could hack around that by creating a single pixel PNG image with #7919CA / 0.8, making it a resizable UIImage and setting that as the background image instead. You can even do that in code pretty easily with CoreGraphics and UIGraphicsContext.