I was getting some quirky behavior as well with this new feature and found that in order to get my Library Colors to actually apply I had to drag my Master Dimension from the sidebar onto the object and choose the "Color by: <<Dimension Name>>" option. Once I did this my Library colors actually worked as expected.
I gave the 'others' and 'null' options a recognisable colour and discovered that it's giving them null colours. So somehow my formula is evaluating to null, even though it's giving me the correct results for my chart.
I've tried wrapping it in another if statement to try to fix it:
Unfortunately it's not working...