For the mercury toxic person, caffiene is bad.

According to a video I have from Dr. Haley, caffiene sort-of "surrounds" the elemental mercury atom and allows it to transport through cell walls (bad). Normally, this only happens (mercury entering through cell walls) when elemental mercury becomes methylated, such as it already is in vaccines.

So... green tea would be bad for the mercury toxic person from this respect.

Green tea does, however, have numerous health benefits. Here's an info sheet:

Green Tea

The good news is... Nature's Sunshine green tea is decaffeinated, so, enjoy!