Steps to repro?
As I said - using a bitmap font, create a UILabel, BBCode is on by default, white tint is set by default, assign some text to the label that include a color tag and the color part gets ignored. The text is all white on the label.
If you switch off the BBCode checkbox, you can see the tag on the label - e.g. "[444444]Test" - and if you switch on the BBCode checkbox you just see the expected "Test", but all white.
Did this throughout 2.x NGUI, so definitely something different, just not sure if it's me or NGUI that's the problem.