David Eagleman's interview in Sydney Australia. First half is about his fiction novel, second half is about synesthesia
Synesthesia, quotes by Sean Day and Ed Hubbard
On the other hand, others report that the colors will interfere when learning basic arithmetic. For example, the colors for 1+2 do not add up to the color for 3.
"It can be both an advantage and a hindrance," Hubbard says. "Some synesthetes seem to get more of the benefits, and others more interference, but both appear to be present."