Bottle peeping is an unusual color name.

In the "Aigame" bottle, a bottle where dye is stored during indigo dyeing, a pale indigo color that is only slightly applied is called bottle peeping.

There is also a theory that the color is like looking into the sky reflected in a bottle.

The light indigo color is called kame-no-peek, and the dark indigo color is called dark indigo.

* It is also written as "jar peeping" and "bottle peeping".