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With ARC, I can no longer cast CGColorRef to id . I learned that I need to do a bridged cast. According clang docs : A bridged cast is a C-style cast annotated with one of three keywords: (__bridge T) op casts the operand to the destination type T . If T is a retainable object pointer type, then op must have a non-retainable pointer type. If T is a non-retainable pointer type, then op must have a retainable object pointer type. Otherwise the cast is ill-formed. There is no transfer of ownership, and ARC inserts no retain operations. (__bridge_retained T) op casts the operand, which must have retainable object pointer type, to the destination type, which must be a non-retainable pointer type. ARC retains the value, subject to the usual optimizations on local values, and the recipient is responsible for balancing that +1. (__bridge_transfer T) op casts the operand, which must have non-retainable pointer type, to the destination type, which must be a retainable object pointer type. ARC will release the value at the end of the enclosing full-expression, subject to the usual optimizations on local values. These casts are required in order to transfer objects in and out of ARC control; see the rationale in the section on conversion of retainable object pointers. Using a __bridge_retained or __bridge_transfer cast purely to convince ARC to emit an unbalanced retain or release, respectively, is poor form. In what kind of situations would I use each? For example, CAGradientLayer has a colors property which accepts an array of CGColorRef</co

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