The 40X Forget-Me-Not™ Tracking Buffer contains an inert blue dye. You have the choice of adding Tracking Buffer to the master mix, to the DNA template, or not to use the tracking buffer in your reactions. Addition of Tracking Buffer to your master mix allows the user to easily distinguish wells containing reaction mix from empty wells. On the other hand, adding Tracking Buffer to your DNA template samples allows you to track which reactions have had template added while you set up your PCR reactions.