I know it could very well be magic since MLP is set in magical world (at least magic returned to G5's world now), however it would also be lovely to have some representation of synesthetes in fiction (and it be positive), and in my opinion Izzy is a very nice character to associate with.

For more info on real world's phenomenon (it's kinda like IRL magic if you ask me): https://en.wikipedia.org/wiki/Synesthesia ^{-^}
I only recently learned of it, and it was sad to realize that most people in my circles (be it online or offline) aren't aware, I hope that'll change someday...

Izzy picture itself is from https://weibo.com/ilovemylittlepony

Material from Sunny Starscout's Book of Adventure is also used.