Keep rolling and mixing up the naphtha/base mix. The more you do it, the more yellow the naphtha will go. I started using a different naphtha for the last few extraction and i was scared that no spice was being pulled out of the bark, as the naphtha was barely yellow. I kept rolling and turning for a few more hours and even though the naphtha was a light yellow I got the highest yield so far! i think the yellow tint does matter some, but not as much as people make it out to be. Best way to test if you have gotten a good amount of spice out of solution is to blow on the naphtha (after pulling of course) and it will go all cloudy white. You know for sure that you have the goods of that happens.