How can I get access to the Main Color and change the alpha color ? How do I know what is the variable of the main color in the shader code ?
If it's Main Color in the Inspector then this is the parameter I should get in the script "Main Color" ?
If the colour is exposed with the name
_Color in the shader code (most defaults are), then you can access it with material.color, using a reference to the material instance you want to change, something like this:
var renderer = GetComponent<Renderer>(); // This getter copies the material to a local instance, // so cache it and remember to clean it up when you're done with it. _cachedMaterial = renderer.material; // Read, modify the alpha, and write back to the material. Color color = _cachedMaterial.color; color.a = 0.5f; _cachedMaterial.color = color;
If it has a different name in the shader code, you can use material.GetColor() or material.SetColor(), passing either the internal name of the colour variable as a string, or an integer ID retrieved via Shader.PropertyToID().
Please remember to take at least a cursory search through the available API documentation or tutorials for basic questions like this - you'll often find your own answer far faster than it takes someone else to type it up for you.