I joined a workshop last year from a bead maker from Ghana, and made my own beads from crushed glass.
We talked quite a bit about the materials used for the beads, and I have to say that all she spoke about was recycled glass items like bottles, jars, etc. I can imagine that the light blue colour can be obtained from white (from Malibu bottles) with a touch of blue glass.
I know that beads are being used to make new beads, but mostly they are melted whole into a new beads, nut completely crushed to achieve a specific colour. Doing it with old trade beads would surprise me.
However, I have not been to Ghana myself, so others who have may know more about the idea of using crushed glass beads to mimic a colour.
You can find more on the workshop and the technique on my blog (scroll down to Krobo beads from Ghana)