Here are two of the oldest polishes I own. Today I swatched Xtreme Wear Gunmetal, and Marine Scene. Before I get into the polishes I just want to say that I think these two colors make a very good combination.
Gunmetal is dark shimmery grey with a blue tint to it. Marine Scene is a turquoise blue, a perfect mermaid color. I can't really judge the formula on these, because they are both many years old and have been used countless times, causing the formula to thicken up. I can however say that, as an avid user of Sally Hansen Xtreme Wear polishes, the formula is very good for the brand overall, especially for the price you pay. Both these polishes were opaque, and matched bottle color, in two coats.