[fmajid]

Soda-lime glass has a greenish hue (look at it sideways). Borosilicate is blueish.

[KingMob]

If you'd read the article, they literally address this. They said the colors are due to unrelated impurities, and are not a foolproof guide.

[s0rce]

This depends on the source of the raw materials, the green is typically from iron and you can have higher purity soda lime glass that is much more clear. I didn't realize there was a visible blue tint in consumer borosilicate glass, I wonder what causes this.