How to change a mesh using a script?

Hello, this is my first UNITY 3D game and i have a "problem" (it's not a problem at all, it's just something i don't no how to do), well i'm making an FPS and i have a code that changes the color of the player depending on his team, the code is like this:

if(teamID==1) mySkin.material.color = Color.red; if(teamID==2) mySkin.material.color = new Color(.5f, 1f, .5f);

i wanna know HOW can I do the same think, but, changing the mesh, not the main color.

PS: I'm using C#.