And yes, I also tested whether black ink comes off. It does.
This was a whole batch of Christmas presents that didn't work for 2012, which sucked. Please share, repin and spread the word so others don't waste their time & money.
If anybody did have success with this some magical way I'd love to hear about it.
Edit: A friend has brought oil-based paint Sharpies to my attention, which are supposed to work on "metal, pottery, wood, rubber, glass, plastic, stone and more" - however - it's not at all clear that these are intended for use on surfaces that will subsequently be frequently washed, and it's not indicated that they are food-safe. Maybe avoiding possible oral contact areas and baking would work with these, I don't know. If somebody does know, please comment.