Bug summary

Incrementing from v3.7 to v3.8 the option to specify a start and end value is no longer functioning when two values are specified. It still works when three are specified.

## This works:
matplotlib.colors.LinearSegmentedColormap.from_list("myMap", ["#000000", "#FFFFFF"])

## This does not:
matplotlib.colors.LinearSegmentedColormap.from_list("myMap", [(0,"#000000"), (1,"#FFFFFF")])

Code for reproduction

matplotlib.colors.LinearSegmentedColormap.from_list("myMap", [(0,"#000000"), (1,"#FFFFFF")])

Actual outcome

Traceback (most recent call last):
File "", line 1, in
File "/Users/dave/.local/share/virtualenvs/projects-t0xU6-ce/lib/python3.10/site-packages/matplotlib/colors.py", line 1065, in from_list
colors : array-like of colors or array-like of (value, color)
File "/Users/dave/.local/share/virtualenvs/projects-t0xU6-ce/lib/python3.10/site-packages/matplotlib/colors.py", line 489, in to_rgba_array
pass
ValueError: '#000000' is not a valid color value.

Expected outcome

<matplotlib.colors.LinearSegmentedColormap object at 0x101e7f520>

Additional information

Worked in 3.7

The issue I think is related to zipped values being passed to r, g, b, a = to_rgba_array(colors).T. A tuple gets passed in rather than a list.

## tuple len 2 fails
>>> matplotlib.colors.to_rgba_array(("#000000", "#FFFFFF"))
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/Users/dave/.local/share/virtualenvs/model_train-t0xU6-ce/lib/python3.10/site-packages/matplotlib/colors.py", line 489, in to_rgba_array
    pass
ValueError: '#000000' is not a valid color value.
## list works
>>> matplotlib.colors.to_rgba_array(["#000000", "#FFFFFF"])
array([[0., 0., 0., 1.],
       [1., 1., 1., 1.]])

Changing r, g, b, a = to_rgba_array(colors).T in colors.py:LinearSegmentedColormap.from_list to r, g, b, a = to_rgba_array(list(colors)).T or similar may fix.

Operating system

OS/X

Matplotlib Version

3.8.0

Matplotlib Backend

MacOSX

Python version

Python 3.10.9

Jupyter version

No response

Installation

None