Ah - Indigo. A very dark, but transparent, blue from Creation is Messy.
Here is another very dark, intense colour that just begs to be used in white-cored cane, twisties, and other ways that need very intensely coloured glasses.
Here you see, from the top, a sample of white-cored cane, the original rod - yeah, might as well be black until you hold it up to the light, and some beads. When you do hold the rod up to a light - it shows more purple - more like violet - than the end result shows.
This is a self-coloured spacer - solid Indigo. You hold it up to the light - you can't see through it. The mark of a good thick wine, or glass. ;-)