Bug summary

The "standard" matplotlib color semantics is that the strings"none" and"None" both mean fully transparent (as can be checked by mpl.colors.to_rgba); the objectNone can sometimes be used to mark a fallback. Because the matplotlibrc format cannot distinguish betweenNone and"None" (due the use of unquoted strings), it normally uses "auto" or "inherit" to mark a fallback.
However,rcParams["legend.labelcolor"] (a relatively recent introduction -- matplotlib 3.5) tries to use "None" as default, and as a result ends up having inconsistent behavior between"None" and"none".

Code for reproduction

frompylabimport*rcdefaults()print(repr(rcParams["legend.labelcolor"]))# default is the string "None"rcParams["legend.labelcolor"]="None";plot([0,1],label="foo");legend()# labels are blackrcParams["legend.labelcolor"]="none";plot([0,1],label="foo");legend()# labels are transparentrcParams["legend.labelcolor"]=None;plot([0,1],label="foo");legend()# labels are black

Actual outcome

See above.

Expected outcome

"None" and "none" should mean the same (likely both should mean "transparent", not so much for usefulness but rather for consistency.

Additional information

I suspect trying to support the objectNone as well here basically cannot be made to work (as long as matplotlibrc uses unquoted strings); the default should switch to be "auto" (or "inherit").

As a further point, the implementation of the rcParams validator_validate_color_or_linecolor seems wrong:

elifisinstance(s,str)andlen(s)==6orlen(s)==8:# (1)stmp='#'+sifis_color_like(stmp):returnstmpifs.lower()=='none':# (2)returnNone

Likely parentheses are missing at (1); also (2) can never hold due to the len() check.
As a side point, 3 and 4-hex color codes ("abc(d)", meaning "#abc(d)", meaning "#aabbcc(dd)") are also not supported by rcParams (this is also the case for the more general _validate_color), even though the normal color machinery does support them. At least this should be documented; I don't know if this can actually be supported without introducing an ambiguity with named colors.

Operating system

macos

Matplotlib Version

3.9.0.dev1542+geb62d6951a

Matplotlib Backend

any

Python version

3.12

Jupyter version

no

Installation

git checkout