Thanks Rini.

Well, those blue strands are still showing some blue tendencies, despite the light red PPD dye, so I'm going to pop one of them into some plain red henna (Yemen) just to see what cooks. If that's what works - then that's the way I'll have to go.

The only other thing I can think of is that the PPD dye was old (which it was - opened for a strand test, and tightly closed and kept in cool shade 2 years ago!) so may not have dyed very effectively.

Back later...