Update README.rst

Author: v0lta

README.rst

@@ -26,7 +26,7 @@ Pytorch Wavelet Toolbox (`ptwt`)
     :target: https://github.com/psf/black
     :alt: Black code style
 
-.. image:: https://static.pepy.tech/personalized-badge/ptwt?period=total&units=international_system&left_color=black&right_color=brightgreen&left_text=Downloads
+.. image:: https://static.pepy.tech/personalized-badge/ptwt?period=total&units=international_system&left_color=grey&right_color=brightgreen&left_text=Downloads
  :target: https://pepy.tech/project/ptwt