I have seen a few pictures of a Red Police Box in the Doctor Who sites, but there are no particulars as to its significance. Can anyone help me out? I am trying to write a fiction based on the Red Tardis.
(The Doctor and Ace return to see the Tardis is now pink.)
ACE: Professor, look what they've done!
DOCTOR: Yes, it looks rather good.
DAISY: You look rather unhappy about something.
DOCTOR: On the contrary. Just admiring your handiwork. [To Ace] Huh, miserable looking thing, wasn't it?
Thanks to @Valorum who found the full video online and also an image:
The significance of it in this story is that they are on a planet where sadness is illegal, and blue is associated with sadness while pink is a more jolly colour. (The episode was intended to be a satire on Thatcherism. Some reviewers have claimed there's a gay subtext in the pink TARDIS, but this theory doesn't seem to be widely believed.)
Other than that, the TARDIS has never canonically been red, outside of jokes and spoofs:
(click for full size version). You're not the only person to think so though.