A related experience... my kids are now taking string lessons, the little angels.
Anyway, under the Suzuki program, they put tape and stickers all over the instrument! I had to swallow my pride and allow it, even though my own 'cello training from a strict German teacher forbade markings of any sort.
I bought a 1/4 size violin off Craigs List, for when my daughter outgrows her 1/8. Step one was removing the stickers, including a huge swath of mole skin bandaging covering the entire chin rest and around to the bottom of the fiddle. So far so good.
Removing the position markers left a bunch of sticky goo on the fingerboard. I decided to clean it up with "goof off" which I think is the same as lighter fluid or xylene.
That's when I found out that the fingerboard was painted black, and the xylene took off the paint.
I think in the final analysis, stripping the fingerboard and cleaning it up left enough black stain to look OK, but it seems much more playable than a painted board. And I am sure that this fiddle will serve my daughter for the time that she uses it.
So I think the moral of the lesson is to avoid anything sticky if one is not 100% certain that it can be removed without solvents. And also, I would now consider cooking oil first before applying xylene.