Set texture grid or diamond view on a plane quad in Unity C#

Question

I am new to Unity C# and I changed material and this changes only the color of a plane.

But how can I have a texture like diamonds or ordonated trianglesenter image description here

I managed to change material of a quad/plane and this changes only the color of a plane.

But how can I have a texture like diamonds or regulated triangles

GameObject plane = GameObject.CreatePrimitive(PrimitiveType.Quad);
plane.transform.position = centroid;
plane.transform.forward = new Vector3(0,90,0);
plane.transform.localScale = new Vector3(5, 5, 5);
plane.GetComponent<Renderer>().material = GreenMaterial;