When I think of "Navy Blue" - this is not the colour I think of.
I think of a dark, somber blue that is based on the colours of the British navy uniform. Wiki agrees with me, and has more to say on the subject, but, as with most of the Italian glass names, I suspect something got lost in translation.
What it is, however, is the colour of the ocean on a stormy day, and that is good enough for me.
Effetre Navy Blue is a streaky blue grey.
It is quite nice.
You know, the more I look at these pictures, the more I wonder if the grey isn't some form of layer/coating/reduction, much like develops on turquoise. Hmmm. I'll have to go soak them in some CLR and see what happens.