Opal

Opal is said to be derived from the word "opalios," which means "to see the change in color."
As its name suggests, opal's unique feature is its "play of color," which changes color depending on the angle from which it is viewed.

Opal is also known as a rainbow stone, but even if we focus only on the blue, there are many different shades of blue in opals.For example, black opals and boulder opals have a blue-on-blue contrast of vivid ultramarine blue play-of-color against a deep blue background. For example, the soft play of mint blue emerges from the pale appearance of a white opal.

I suspect there are more blue hues in opal than there are names for blue in the world.