What’s the Difference between Overdyed and Variegated Threads?

copyright Napa Needlepoint

Anne asked me “Is there a clear distinction between variegated and overdyed threads? I seem to remember from some source that variegated threads are variations/shades of the same color and overdyed are threads which are multicolored. Is that correct?” What the terms actually mean and how we use them are two different things. In precise [...]