/usr/share/matplotlib/mpl-data/stylelib/ is in python-matplotlib-data 1.5.1-1ubuntu1.
This file is owned by root:root, with mode 0o755.
..
/usr/share/matplotlib/mpl-data/stylelib/bmh.mplstyle
/usr/share/matplotlib/mpl-data/stylelib/classic.mplstyle
/usr/share/matplotlib/mpl-data/stylelib/dark_background.mplstyle
/usr/share/matplotlib/mpl-data/stylelib/fivethirtyeight.mplstyle
/usr/share/matplotlib/mpl-data/stylelib/ggplot.mplstyle
/usr/share/matplotlib/mpl-data/stylelib/grayscale.mplstyle
/usr/share/matplotlib/mpl-data/stylelib/seaborn-bright.mplstyle
/usr/share/matplotlib/mpl-data/stylelib/seaborn-colorblind.mplstyle
/usr/share/matplotlib/mpl-data/stylelib/seaborn-dark-palette.mplstyle
/usr/share/matplotlib/mpl-data/stylelib/seaborn-dark.mplstyle
/usr/share/matplotlib/mpl-data/stylelib/seaborn-darkgrid.mplstyle
/usr/share/matplotlib/mpl-data/stylelib/seaborn-deep.mplstyle
/usr/share/matplotlib/mpl-data/stylelib/seaborn-muted.mplstyle
/usr/share/matplotlib/mpl-data/stylelib/seaborn-notebook.mplstyle
/usr/share/matplotlib/mpl-data/stylelib/seaborn-paper.mplstyle
/usr/share/matplotlib/mpl-data/stylelib/seaborn-pastel.mplstyle
/usr/share/matplotlib/mpl-data/stylelib/seaborn-poster.mplstyle
/usr/share/matplotlib/mpl-data/stylelib/seaborn-talk.mplstyle
/usr/share/matplotlib/mpl-data/stylelib/seaborn-ticks.mplstyle
/usr/share/matplotlib/mpl-data/stylelib/seaborn-white.mplstyle
/usr/share/matplotlib/mpl-data/stylelib/seaborn-whitegrid.mplstyle