Change color of 3D Text during runtime.

How to change the color of 3D Text for the text shader has been applied.

GetComponent<Renderer> ().material.shader = Shader.Find("Transparent/Diffuse"); 
GetComponent<Renderer>().material.SetColor("_SpecColor", Color.white);

The color of 3D text remain black and it is not changing to white.

How to change the color of 3D text to white for which shader has applied?

For example :