readme: fix a typo

Author: Mingshen Sun

README.md

@@ -49,7 +49,7 @@ More details about each features, roadmap, and building process can be found her
 
 MesaPy enhances PyPy in security. Compared to CPython (as known as Python),
 MesaPy provides a comprehensive security protection. Following figure illustrates
-MesaPy's design and implementation. Blocks highlighted in read means unsafe
+MesaPy's design and implementation. Blocks highlighted in red means unsafe
 components, while blue blocks represent safe components. MesaPy aims to
 protect Python runtime by our security hardening.