What ingredients are currently used in the manufacture of ink for Safrus? Is there a different formulation for the paint that is used to dye tefillin straps/boxes?
This seems to be a good page to see.
For a more comprehensive source, see the Mishkenos Yaakov.
For retzuah paint, you can just use shoe polish. It doesn't require d'yo.
The above linked pages contain recipes for the ink used by most sofrim today, known as מי עפצים וקנקנתום -- oakgall juice and ferrous sulfate. This post, written by a very qualified sofer has a recipe.
The Sta"m Forum has a page with a well tested recipe for STA"M ink almost identical to the one in Kol Sofrim. I can't vouch for it because I buy ink, but the person who posted it is a professional who has written several Sifrei Torah.