Colorize the PS4 prompt?

With the option set -x, each command is echoed to STDERR before execution, prefixed by the expanded $PS4, with the first character being repeated according to the call stack depth. I want the output of the $PS4 prompt to be colorized. I.e. where (set -x; ls -l) will currently print + ls -l I want an output \033[90m+ ls -l\033[0m \ \ \ `- Reset color `- Muted gray However, with PS4 being printed before echoing the command, I can't think of a method to reset the color with \033[0m *before* the command is executed. Is it possible to do this somehow?