Bug summary

LineCollection doesn't have a get_gapcolor or set_gapcolor, so gapcolor doesn't work in plotting methods that return LineCollections (like vlines or hlines).

Code for reproduction

fig, ax = plt.subplots(figsize=(1,1))
ax.vlines([.25, .75], 0, 1, linestyle=':', gapcolor='orange')

Actual outcome

File ~\miniconda3\envs\prop\lib\site-packages\matplotlib\artist.py:1186, in Artist._internal_update(self, kwargs)
-> 1186     return self._update_props(
   1187         kwargs, "{cls.__name__}.set() got an unexpected keyword argument "
   1188         "{prop_name!r}")

AttributeError: LineCollection.set() got an unexpected keyword argument 'gapcolor'

Expected outcome

Additional information

I think the easiest fix is probably add set_color and get_color to LineCollection, modeled on get_color and set_color

Matplotlib Version

3.7.0.dev1121+g509315008c