.NET Framework: Understanding Green Bits and red Bits

In lots of articles about .NET Framework 3.0/3.5 you might find the term called Green bits or Red bits. What is that all about? Must read this article to understand the architecture,  https://www.danielmoth.com/Blog/2007/06/net-framework-35.html 

Let's also use the picture from that blog

Namoskar!!!