what an odd coincidence.  Yesterday I noticed that Rudy's tongue was
purple!  It's normally a very light pink.  I looked in his mouth and
his gums and lips were still light pink like normal, so I figured it
wasn't heart related and forgot all about it until your post.  Rudy is
3 years old and healthy.  I'll be curious to know what your vet says
about it.

what an odd coincidence.  Yesterday I noticed that Rudy's tongue was
purple!  It's normally a very light pink.  I looked in his mouth and
his gums and lips were still light pink like normal, so I figured it
wasn't heart related and forgot all about it until your post.  Rudy is
3 years old and healthy.  I'll be curious to know what your vet says
about it.

It might be from the meds or something he ate while there. (My tongue
turns purple when I eat blueberries.)  

A purple tongue could also be an indication of shock (a drop in blood
pressure and the blood not picking up enough oxygen).  What color are
his lips and gums?  If they're a healthy normal color, I wouldn't worry
too much about it, but I would monitor it closely.  

Another possibility is that he's developed a fungal infection on his
tongue.  I've never heard of a cat with a mouth fungus, but we people
sometimes get them when antibiotics knock out the beneficial bacteria in
our mouths or when stress has weakened our immune systems, so I'd guess
the same thing could happen in a cat.

One of my cats toung and mouth got purpleish when he wasn't breathing well.
An hour on oxygen and some other treatment helped.

Another had suspected liver problems from starving herself (due to being
dumped for the crime of being FIV). Both are better now.

I suggest having a vet look at the toung, my vet though both of my purple
toungs were pretty serious at the time.

ron