gh-138772: Improve documentation for turtle color functions

[serhiy-storchaka]

Use multiple signatures for clarity.
Explain different forms of bgcolor() in details.

• Issue: Turtle dot function not accepting color parameter. #138772

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📚 Documentation preview 📚: https://cpython-previews--139325.org.readthedocs.build/

[encukou]

Do you think it could it be better to link to a more commonly used function, rather than repeat all the info?

Suggested change

	Four input formats are allowed:
	``bgcolor()``
	Return the current background color as color specification string or
	as a tuple (see example). May be used as input to another
	color/pencolor/fillcolor/bgcolor call.
	``bgcolor(colorstring)``
	Set the background color to *colorstring*, which is a Tk color
	specification string, such as ``"red"``, ``"yellow"``, or ``"#33cc8c"``.
	Set or return background color of the TurtleScreen.
	``bgcolor((r, g, b))``
	Set the background color to the RGB color represented by the tuple of
	*r*, *g*, and *b*.
	Each of *r*, *g*, and *b* must be in the range 0..colormode, where
	colormode is either 1.0 or 255 (see :func:`colormode`).
	``bgcolor(r, g, b)``
	Set the background color to the RGB color represented by *r*, *g*, and *b*. Each of
	*r*, *g*, and *b* must be in the range 0..colormode.
	The arguments use the same format as :func:`fillcolor`.

[serhiy-storchaka]

Should not both refer to pencolor()? Although bgcolor() is a method of different class than pencolor() and fillcolor().

And we need to repeat this in the docstrings.

[serhiy-storchaka]

Docstrings also require an update.

Docstrings were outdated and incorrect -- all these functions now return a tuple instead of "#"-string.

[serhiy-storchaka]

Should not both refer to pencolor()? Although bgcolor() is a method of different class than pencolor() and fillcolor().

And we need to repeat this in the docstrings.

[miss-islington-app]

Thanks @serhiy-storchaka for the PR 🌮🎉.. I'm working now to backport this PR to: 3.13, 3.14.
🐍🍒⛏🤖

[bedevere-app]

GH-140047 is a backport of this pull request to the 3.14 branch.

[bedevere-app]

GH-140048 is a backport of this pull request to the 3.13 branch.