Reading in color is a new method for training letter-color associations that are typically found only in grapheme-color synesthetes. It involves an implicit form of training that has potential for long-term associative training methods because the training is a byproduct of reading and any text can be colored.
Colizoli, O., Murre, J. M. J., Rouw, R. Training Synesthetic Letter-color Associations by Reading in Color. J. Vis. Exp. (84), e50893, doi:10.3791/50893 (2014).