Summary

Some color rcParams that can fallback to another rcParam use "auto" to indicate that fallback (lines.markerface/edgecolor, boxplot.flierprops.markerfacecolor, axes.titlecolor, savefig.face/edgecolor), whereas others use "inherit" (legend.face/edgecolor, x/ytick.labelcolor).

There's also legend.labelcolor, which uses "None", but that's a much more complicated case (#28153).

Proposed fix

This should be made consistent. Safest (and not really an issue) would be to just support "auto" and "inherit" with the same meaning for all those rcParams; it would also be possible to pick a single winner, use it consistently, and deprecate usage of the other, although I'm not really sure it's worth the annoyance.