Change silhouette color on a metaballs shader

Hi, I need help with a problem I have.
I'm making a game with metaballs and I want the edges to be the same color as the squares.

I've tried a few things but I can't get it.
I don't specialize in shaders, I just know very basic things.

I basically took the code from this project and applied it to mine: http://patomkin.com/blog/metaball-tutorial/