While integrating a tox based job in Jenkins (which has a dumb terminal) I was looking for a way to force color output. Looking at _py/terminalwriter.py , it looks up the environment variable PY_COLORS. A value of 1 would enforce color, a value of 0 would disable color. The global override the TERM value.
It would be nice to have PY_COLORS documented in the tox documentation.
py-trunk doc update request is: https://bitbucket.org/hpk42/py-trunk/issue/138/py_colors-env-is-undocumented