Панды устанавливают условие многочисленные столбцы
conditions = [
.....: (df['col2'] == 'Z') & (df['col1'] == 'A'),
.....: (df['col2'] == 'Z') & (df['col1'] == 'B'),
.....: (df['col1'] == 'B')
.....: ]
.....:
In [214]: choices = ['yellow', 'blue', 'purple']
In [215]: df['color'] = np.select(conditions, choices, default='black')
In [216]: df
Out[216]:
col1 col2 color
0 A Z yellow
1 B Z blue
2 B X purple
3 C Y black
NP