Thanks Paul__B, wow - so difficult trying to explain something while using the wrong picture 
Wish I had one of these to do a quick test, but I believe there's a large Vf difference for each colour (due to dye material). They specify 9-12V and I don't "think" its due to manufacturing tolerances. They should specify Vf and max current for each colour.
A simple way to check would be to apply a constant low current ... like just using 330 OHM connected in series to 12V to drive each colour then measure the different Vfs.
Seems that manufacturers don't want to specify too many details ... could hurt sales.
Oh well, good luck JoeN with your testing!