I was trying to change the colour of a piece of stained glass on my console by using a tardis panel, but I can't change the data value! How could I add the data value?

Here's an informative video! 

Actually, as I brought out in that video, as far as I'm aware, there is no way to place different colors of stained glass, or similar colored blocks like wool, with the TARDIS panel because the command does not allow you to place a block with meta data, or the data value.

Unless I overlooked something, you may be stuck with ordinary glass and white stained glass.

However, you could try having the panel place some redstone down that would activate a command block that would set the stained glass for you.