All glass aquariums are green tinted due to the lead in the glass, although it's more pronounced on thicker pieces then on thin ones. The exception to this is special low-lead glass, sold under the trade name of starphire. It's a good bit more expensive, so it only ever pops up on custom tanks.
FWIW, I have a starphire tank and I consider it money well spent.
From what I understand it is not tinted, just as they get larger the glass has a greenish look to it. You can avoid this by paying more for starfire glass. Following is a short link from a previous post.
Yeah, the green tint is almost undetectable with untrained eye for thin glass. I am in the process of getting rid of the blue tint of the water by using special water molecule with a different vibration mode (seriously, I do know how to make water without blue tint, PM me if interested).
Yes, its the minerals in the water.
BTW, what is the point in taking the blue out of the water when most reefers are adding blue by use of actinic lighting or 20k bulbs? :lol: