Even the inside of modern tanks like the M48, M60, M551, M1/A1/A2 are white today.
Here is a link to an album of the interior of the M3 Lee (basically the same tank).
http://www.toadmanstankpictures.com/lee.htm
While this is a modern M88A1 recovery vehicle, you cansee that just about everything is painted white inside, treadplate included.