Which one is which?

Been a bit of a a busy week due to the current viral/flu bug taking its toll on all members of staff ( docs, nurses and receptionists) so looking forward to a quiet weekend.
These are sharp bins that we use for getting rid of needles, syringes and other bits of high risk clinical waste. They are helpfully colour coded to ensure the right stuff goes in the right bin. This simple system is completely beyond me and I'm always sticking stuff in the wrong bin.