Look it up. It's a kind of natural sweetener the US sugar industry doesn't like, but although it's extremely sweet and extremely cheap the fact is its sweetness is delayed. ...but if you add a bit of sugar you get the initial sweetness and then the stevia prolongs the effect. Bodybuilding products, normally whey mixes, sometimes use stevia as a sweetener, but it's occasionally used for other reasons in other products. Stevia isn't usually an off-the-shelf sort of thing in the US. We had to mail-order ours, but we hardly use it.
Teal is actually a bit bluer, perhaps darker than that.