Update README.md

Author: jankupczyk

README.md

@@ -2,7 +2,7 @@
 ## Zombioo is a free 2D game written in python using Pygame
 
 <p align="center">
-  <img src="https://img.shields.io/github/issues/jankupczyk/Zombioo?color=red&style=for-the-badge" alt="jankupczyk" />
+  <img src="https://img.shields.io/github/issues/jankupczyk/Zombioo?color=critical&style=for-the-badge" alt="jankupczyk" />
   <img src="https://img.shields.io/github/stars/jankupczyk/Zombioo?color=success&style=for-the-badge" alt="jankupczyk" />
   <img src="https://img.shields.io/github/forks/jankupczyk/Zombioo?color=success&style=for-the-badge" alt="jankupczyk" />
   <img src="https://img.shields.io/github/license/jankupczyk/Zombioo?color=important&style=for-the-badge" alt="jankupczyk" />