I didn't know you could catch your angel.
It's not a matter of timing. It's just with the shadows, you'll hit the bell so many times you don't know what color it's going to change to next, or if it'll even land on a color. It's also a pain when you're trying to keep a bell in the air while fighting enemies, or if an enemy gets in your line of fire, and you miss hitting the bell.
It's a fun game though, don't get me wrong.