Has this already been asked and answered anywhere? I jsut told someone I was tickled red about something, jsut to be different, and then got to wondering about this…
Amazingly, not too many normal sources seem to tackle this. I will go down to my public library tomorrow and report back.
Is this a trick question? It seems too obvious.
When a person is tickled, esp. a lot, they blush.
You know, turn pink.
Peace,
mangeorge
Probably the only place where one could be “tickled red” would be communist countries.
Tickled green - Ireland
Tickled yellow - Urologist’s office (or should that be trickled)
(I know this is something of a hijack, but your question has been answered)
“Tickled Pink” is actually a trademarked slogan of Dr.Pinky.Inc. (involving the dexterous use of my smallest digit.)
Try it, you’ll like it.
“I’ve got more talent in my little pinkie than he has in his whole thumb!”
WAG: Tickling, in addition to inducing laughter, often causes capillary dilitation, causing a rosy-cheeked, or flushed appearance. I don’t know if it’s the derivation of the phrase, but it’s the only thing I can think of
Told ya! 
Somebody’s been digging in the old threads.
Peace,
mangeorge