We had a tour of the Wedgewood/Royal Doulton factory a few years ago.
The Royal Doulton bone china is fired once, painted, glazed and fired again.
The glaze prevents the paint from changing color when fired.

The Wedgewood porcelain is painted before firing (I guess you cant fire it twice?)
The ink/paint/dye comes out a totally different color. The gold paint, for example is black before firing.

When you buy 'seconds' of Royal Doulton you have to be careful because if they notice a fault before the 2nd firing they dont bother. Then the paint starts coming off in the dishwasher