Calculated Colours in Bar Charts

[#1]

I have a stacked bar chart. This shows proportions against three values, 'Yes', 'No' or 'N/A' (field "Satisfaction"). These are also represented by -1, 0 and 1 (field "Satisfied").

To make sure, especially when drilling down, that colours are Green, Red and Yellow respectively, I am trying to use the Color Area Base Color Calculated feature from the Colors tab. Neither of my formulae work:

=if(Satisfied=-1,rgb(0,255,0),if(Satisfied=0,rgb(255,0,0),rgb(255,255,0)))
=if(Satisfaction='Yes',rgb(0,255,0),if(Satisfaction='No',rgb(255,0,0),rgb(255,255,0)))

When I apply either of these formulae to the background colour of the cells of a straight table object, they both work just fine.

Is this a bug in Version 9, or just my formulae?

It would appear that whatever variables I am using for my colour formulae, they are null. Is there a way to perpetuate a value in a chart without it appearing in the chart? Seems to make the calculated colour pretty redundant if not.

[#2]

alternative calculation that doesn't work:

=if(isnull(Satisfaction),rgb(255,255,0),if(Satisfaction='Yes',rgb(0,255,0),if(Satisfaction='No',rgb(255,0,0))))

renders as rgb(255,255,0)

[#3]

Further testing suggests that the formulae work when the entire bar is a single value, although the formulae don't work on an unstacked bar.