John,
There are a variety of techniques, one of the most popular being to add a drop or two of blue food color and a drop or two of green (have to experiment to get the shade you want) to Future floor polish. I use the clear paints instead of food color when I do tinted windows, but the principle is the same. The fundamental idea is to use some sort of carrier so you can build up the pigment in a controlled fashion until you get the level of tinting you desire.
The angle on this photo isn't the best for illustrating, but you can just make out how subtle an effect you can get with this technique:
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There is definitely some trial and error involved in arriving at a technique that works well for you.
Good luck!