setting legend values according to categorical data in matplotlib

Question

I'm trying to set the legend according to categorical values set for color but it's not working.

import matplotlib.pyplot as plt
colors = finalDf['sales'].astype('category').cat.codes
scatter = plt.scatter(x= finalDf['principal component 1'],
            y= finalDf['principal component 2'],
            c = finalDf['sales'].astype('category').cat.codes)
plt.xlabel('PC1')
plt.ylabel('PC2')
plt.legend(labels=list(finalDf['sales'].unique()))
plt.show()

(https://i.stack.imgur.com/YwSoG.png)

I tried various combinations of the 'sales' data columns but it was in vain. I want to know if there is a solution other than using seaborn library as the task recquires matplotlib. Thank you