We too have experienced this problem, when EncodeHiddenValue="false" it affects the font colours when you send.

 

Any font which starts with #3 is turned in the & ie #33cccc will become &3cccc and then inturn be totally  removed from the span by the editor tag when you go to re-edit.

 

I can confirm that your online example does the same. Try the using the ocean blue colour - five in from the left and three down. See the problem??