Instantiating objects with their own materials

Hello, I am currently working on a firework system. I'm stuck at a part where I would like to create a new material for each "flare" in the firework (which is a prefab being instantiated), and I have tried several different methods, none of which seem to work. I have come to understand that using gameObject.GetComponent().material will create a new instance of the sharedMaterial, however, I can't seem to do this without unity freaking out with the error of "Instantiating material due to calling renderer.material during edit mode. This will leak materials into the scene. You most likely want to use renderer.sharedMaterial instead." But I do want each of my prefabs to have their own material so I can adjust them individually as the firework is being played. Here's the firework class:

 using UnityEngine;
 using UnityEditor;
 using UnityEngine.Serialization;
 using System.Collections;
 using System.Collections.Generic;
 
 [ExecuteInEditMode]
 public class Firework : MonoBehaviour
 {
     public int
         numberOfFlares = 50;
     public float flareSize = 1.0f;
     public GameObject flarePrefab;
     public Color
         colorOnRising;
     public bool
         gravityOnRising = false;
     public Vector3 startingVelocity = new Vector3 (0, 1000, 0);
     public float
         explodeTime = 100f;
     public float explodeForce = 50f;
     public bool gravityOnExplode = true;
     public float flareLifeTime = 5f;
 
     private float timePassed = 0.0f;
     private float timeSinceLaunch = 0.0f;
     private float timeSinceExplostion = 0.0f;
 
     private List<GameObject> flares = new List<GameObject> ();
 
     public enum Phase
     {
         NotLaunched,
         Rising,
         Exploded
     }
 
     public Phase
         currentPhase = Phase.NotLaunched;
 
     public void Launch ()
     {
         if (currentPhase == Phase.NotLaunched) {
             //ready to launch!
             Debug.Log ("Launched!");
             currentPhase = Phase.Rising;
             for (int amount = 0; amount < numberOfFlares; amount++) {
                 GameObject go = (GameObject)Instantiate (flarePrefab, gameObject.transform.position, gameObject.transform.rotation);
                 flares.Add (go);
             }
             foreach (GameObject go in flares) {
                 go.transform.localScale = new Vector3 (flareSize, flareSize, flareSize);
                 go.GetComponent<MeshRenderer> ().material.SetColor ("_Emission", colorOnRising);
                 go.GetComponent<Rigidbody> ().useGravity = gravityOnRising;
                 go.GetComponent<Rigidbody> ().velocity = startingVelocity;
             }
         }
     }
 
     public void Refresh ()
     {
         Debug.Log ("Refreshed!");
 
         bool launchAfterRefresh = (currentPhase != Phase.NotLaunched);
 
         timePassed = 0;
         currentPhase = Phase.NotLaunched;
         foreach (GameObject go in flares) {
             DestroyImmediate (go);
         }
         flares.Clear ();
 
         if (launchAfterRefresh) {
             Launch ();
         }
 
     }
 
     public void Stop ()
     {
         Debug.Log ("Stopped");
 
         currentPhase = Phase.NotLaunched;
         Refresh ();
     }
 
     // Use this for initialization
     void Start ()
     {
         Debug.Log ("Started!");
 
         Refresh ();
         Launch ();
 
     }
     
     // Update is called once per frame
     public void Update ()
     {
         foreach (GameObject go in flares) {
             go.transform.LookAt (Camera.main.transform.position);
         }
         if (currentPhase != Phase.NotLaunched) {
             timePassed += Time.deltaTime;
         }
     }
 }