Does Latin "pingo" to paint relate to "pix" tar by analogy with "pango" to agree and "pax" peace?
Disclaimer: I'm not even close to expert in Proto-Indo-European, so maybe I'm missing something important.
According to this database:
The source, according to the site is:
Walde-Pokorny's dictionary [possibly the Indogermanisches etymologisches Wörterbuch], compiled by S. L. Nikolayev
... which is a pity, because it was fun to think that the verb to paint and pitch/tar were etymologically related in Latin. (and makes some sense).