Petroleum Blue

I was chatting with my sister, on IM, and she now wants a petroleum blue shawl to cover her shoulders when she's wearing her jeans dress.
What the heck is petroleum blue? I searched the web, and got two TOTALLY different shades of blue. Who wants gasoline blue, gasoline is expensive enough already, and now to wear it, too????
She said it's like oil blue, or gasoline blue, very fashionable in Europe now. Yeah, now I need the yarn in PETROLEUM BLUE thank you very much. WHERE????? which yarn????

I told her that she can have a black one.