"Opal" seems to be the term used by either the Czechs or the Czech importers to refer to a slightly clouded, milky version of various hues - pink, red, purple, blue, yellow, green...

The translucency is not uniform, and appears more as cloudy swirls in the glass.

The beads in the photo are maroon opal - my camera made the red too bright, they face up maroon. But hopefully the difference in transparency from bead to bead is visible.