ValueError: 'c' argument must be a color or a sequence of colors

ValueError: ‘c’ argument must be a color or a sequence of colors

$ python -c "import matplotlib.pyplot as plt; import numpy as np; plt.scatter([1,2],[3,4], c=np.array([[1,2,3]]))"
Traceback (most recent call last):
  File "<string>", line 1, in <module>
ValueError: 'c' argument must be a color or a sequence of colors

Why this happens

The c argument expects a single color spec or an array of colors matching points; wrong shape or values cause errors.

Fix

Provide a valid color string, RGB(A) tuple, or a 1D array matching data length.

Wrong code

import matplotlib.pyplot as plt
import numpy as np
plt.scatter([1,2],[3,4], c=np.array([[1,2,3]]))

Fixed code

import matplotlib.pyplot as plt
import numpy as np
plt.scatter([1,2],[3,4], c=['red','blue'])
plt.show()