I use French vanilla instead of Dense White or White Opaque unless I need to use a color with lead or copper, which are most of the pinks and purples, and of the some blues and greens. Bullseye has a color reaction chart on their website that tell you what colors react with other colors....
http://www.bullseyeglass.com/methods...ity-chart.html
The French Vanilla looks white and it is easier to work with than the other white so I use it whenever I can.