Looking at originals I would suggest white was what was originally used
As far as paint verses ink I would choose what best reproduces the look and that is not always what was originally used. Having done a fair number of these things I would go with paint with the spray can and magazine method just for the final look. Believe with ink I would get a more muted finish and too perfect and complete of a looking stamp in the end
Of course you can practice/test on a few unrestored curved surfaces first to see which one looks better to you