my eggs didn't turn out right...

I tried to dye easter eggs with dye made from purple cabbage. I googled it and read lots of tips but it didn't work. I hardboiled the eggs in regular water as I read the cabbage dye works best cold. Then I boiled up the cabbage and added a little cream of tartar and white vinegar. I let the eggs soak in that liquid after it cooled but they didn't change color...so I added a bit more vinegar and cream of tartar. The eggs did get a light blueish purple...but the eggs surface was gritty and when I wiped them the color easily came off.

So has anyone successfully used a dye like this for easter eggs? I only dyed four today for my test round so I am going to dye the rest when I get it figured out. Thanks so much!