I imagine that the multiple infinities in the physicists' sense intersect and have vertices. It'd be something like saying that 'the infinite set of even integers exists within the infinite set of real numbers,' and also in this case (infinity a) < (infinity b).

Seeing letters/numbers in the mind as different colors is actually a really interesting phenomenon - it's called "synesthesia," and we all do it to some degree. There was a book written in the early 20th century by a Russian psychologist A.R. Luria who made a cooperative study with a man who was widely regarded for his perfect memory / calculation abilities / and absolute pitch who was profoundly synesthetic - saw sounds as colors, would often describe the voice of an interlocutor as say a "crumbly yellow." It's called "Mind of a Mnemonist," and it's probably available for free online these days. http://sites.google.com/site/russianpsychologia/