one characteristic of beads such as these- if the "fibres" are narrow drawn-out hollow bubbles then they can be coloured by saturating with liquid ink or varnish that seeps into the hollows by capillary attraction, and then can't rub off. i have a few where this appears to be the case, including satin effect bugles and rocailles...and also moulded czech "Atlas" beads from the 1950-60s of solid dense coloured satin glass, not with drawn bubbles, for comparison.
will try to locate the examples and show images when i get a minute.