Confession, the old colour looked way too deep in shadow so I removed the colour. But the fabric went a blotchy silver with a few blue patches. So to the shame pile it went.
I finally used a tiny tiny tiny amount of turquoise iDye poly on the dress (to brighten the hem mainly) and that went well so I topped up with enough blue to dye the cape and basically use the turquoise and green (released from the hem) to knock the purple out of the dye.
Voila! The wind also kicked up beautifully.
Just never ask me to iron crystalline tulle ever again. Ever.
Ever.