Can Synesthesia be Learned?

From: Teach Yourself Synesthesia? I Don’t Think So!- The Fallible Mind (blog on Psychology Today)-Richard E. Cytowic, M.D. 

This blog discusses a study done in Amsterdam trying to prove that Synesthesia could be learned by setting up "synesthesia in reverse," changing the physical world. They did this by giving non synesthetes a book with letters e, s, and t printed in different colors. The result was that the non synesthetes ended up associating those colors with the letters and thus this became the first evidence that synesthesia was something that could be learned. 
I did not agree with how the study approached synesthesia and didn't think it made sense. First of all, color grapheme synesthetes unintentionally associate letters, words or numbers with colors. These colors are not chosen by someone else for them or strategically placed for them to associate.  We can deliberately learn anything whether we have synesthesia or not, that's pretty much all the study proved- it did not prove that we can learn to be synesthetes. synesthesia is a condition possessed only by those born with the synesthesia gene or who have had some sort of brain damage like a stroke and their brain repaired itself and ended up mixing certain regions of perception.