Effect Shader - Tutorial or explanation?

[yojeff]

I'm looking for a tutorial to understand how an Effect Shader works.

 

I want to create a membrane shader on an NPC. I found one that works, but I don't know how it works?

 

So I want a color effect on an NPC, similar to the one when you move an armor rack in the settlement system. The shader I found has "Source Alpha" as both the Source and the Dest Blend Mode. Fine, but what is the "Dest Alpha" you can choose? It then applies a color. I thought Alpha was about transparency?

 

Thanks!