The current color code is pretty much the same as GalCiv 2, in fact imho, it should be left as it was in GalCiv 2, it was perfect.
White : Treasury in the positive no deficit: ( Used to be Green In GalCiv II )
Yellow: Tresury in the positive with deficit
Orange: Treasury in the negative with no deficit. ( orange is missing in GalCiv III now )
Red : Treasury in the negative With deficit
The claim that White and yellow might be hard to tell apart on some monitors might be genuine although I do not have this problem here. For this reason I support the use of Green.