At the end of Turn Left, when the Doctor finds out about Bad Wolf, he runs back to the Tardis. The interior has turned completely red.
I know the out-of-universe reason is mood lighting for the dramatic finale ups the ante. But has there ever been a convincing in-universe explanation put out?
The start of the following episode, The Stolen Earth, has the Doctor and Donna running out of a red Tardis and then running back into a red Tardis moments later. But by the time of the next scene it's back to its usual yellowish colour scheme. So I'd guess that it was red for only 2-3 minutes, tops.
What, if anything, explains the Tardis's sudden and transient change of colour?