Makes me wonder if young children generally have some form of Synesthesia, when the brain still develops, that then subsides in most adults.

While I had practically forgotten it until you mentioned it, I had similar experiences, for example the french song "au clair de la lune" always evoked the same, very vivid (but rather abstract) picture in my mind. To my child mind, it was so intense that the song was that picture to me.

Nowadays this doesn't happen...