iDye changing garment color update

Initially, I used iDye to re-dye a couple faded black cotton sweaters......and it worked beautifully. 

THEN.... I got the idea to change the color of some knitwear that I seem to never wear. I like the pieces but don't wear them because of the color ......or have nothing really to go with them. 

So my great idea came with some mixed results.  The cotton knits took a couple of goes at it to get the saturated color that I wanted.......and now have a few pieces that have gone from dust collectors to vital wardrobe pieces.   Love this!

The mixed result came from a silk/linen blend cardi that was a pale pale blue.  Lovely in its own right, but I never wore it.  If it were black I knew I would wear it all the time....right?

So in the iDye instructions, you add salt if the garment is cotten or linen and you add white vinegar if it is silk.   What to do?  My cardi is silk and linen.  So my logic said to add both..... do I hear shreeks and screams?

Yes, that is what I did, added both and my pretty pale blue cardi that I never wore is now a funky plum color.  Not horrible, but its plum and not black. I'm not exactly sure what I did wrong and  why my black dye produced a plum color.  I may give it another try later.....but for now I am a little "gun-shy".  Perhaps...some research is involved......