Click on the print view of a saved illustration and click on the link called "share illustration."  Type in the email address of the person you want to share the illustration with and add any comments.  Clicking on the "Share Illustration" button will email your collaborator.

An alternative way to do the same is to copy the URL of the print view page of that illustration and send it to your collaborator via email/IM/tweets.

Note that the collaborator must already have access to Cytobank and to the experiment in question.