Material & Shader

using UnityEngine;

public class MaterialController : MonoBehaviour
{
  Renderer rend;

  void Start()
  {
      rend = GetComponent<Renderer>();

      // sharedMaterial: shared with every object → no extra copy
      rend.sharedMaterial.SetColor("_BaseColor", Color.red);

      // material (not shared): a private copy for this object
      rend.material.SetFloat("_Metallic", 0.9f);
      rend.material.SetFloat("_Smoothness", 0.8f);
  }

  public void Flash(Color color)
  {
      // Flash trick: set emission color
      rend.material.SetColor("_EmissionColor", color * 2f);
      DynamicGI.SetEmissive(rend, color * 2f);
  }
}

using UnityEngine;

// Color each instance differently WITHOUT breaking GPU Instancing/Batching
public class InstanceColorizer : MonoBehaviour
{
  static readonly int ColorID  = Shader.PropertyToID("_BaseColor");
  static readonly int EmitID   = Shader.PropertyToID("_EmissionColor");

  MaterialPropertyBlock mpb;
  Renderer rend;

  void Awake()
  {
      rend = GetComponent<Renderer>();
      mpb = new MaterialPropertyBlock();
  }

  public void SetColor(Color color)
  {
      rend.GetPropertyBlock(mpb);          // Read current state
      mpb.SetColor(ColorID, color);       // Change color
      rend.SetPropertyBlock(mpb);          // Apply — no new Material
  }

  public void SetEmission(Color emitColor)
  {
      rend.GetPropertyBlock(mpb);
      mpb.SetColor(EmitID, emitColor);
      rend.SetPropertyBlock(mpb);
  }
}