@samcarter yes, the definition of \normalcolor has changed (to keep track of the dot color) and if xxcolor is loaded too the patching of \normalcolor pdfrender fails. (very curious patching code in pdfrender ...).
@DavidCarlisle ^^ I think we should use the sword again and move pdfrender out of oberdiek.
@samcarter well it loads xxcolor which redefines \XC@mcolor so that it now contains \colorlet{XC@mixtmp}{.} and that fails in the preamble. But pdfrender should simply not try to patch \normalcolor like this, it is relying on internals.
@DavidCarlisle I have split up. And I found a (plaintex) bug in ltxcmds. I wonder what that mean for the plaintex usage of pdfrender if nobody complained in three years that it doesn't work ... ;-)
