L-system with colour /size/ rotation variation

LSystem.cs

using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using UnityEngine.SceneManagement;



public class LSystem : MonoBehaviour
{
    [System.Serializable]
    public class Customisation
    {
        public Gradient colours;
        public string axiom = "A";
        public string rule = "A[AA]";
        public int iterations = 3;
        [TextArea]
        public string output;
    }
    int index = 0;
    string currentLetter;
    public GameObject branch;
    public GameObject berry;
    GameObject currentBranch;
    string instructions = "A";
    List<Vector3> positions = new List<Vector3>();

    public Customisation custumisation = new Customisation();

    private void Start()
    {
     

        instructions = custumisation.axiom;
        currentBranch = Instantiate(branch, transform.position, Quaternion.identity);
        positions.Add(currentBranch.transform.Find("top").transform.position);
        currentBranch.GetComponent<SpriteRenderer>().color = custumisation.colours.Evaluate(Random.Range(0f, 1f));
        currentBranch.transform.parent = transform;
        while (custumisation.iterations > 0)
        {
            Iterate();
            custumisation.iterations--;
        }
    }


    void Iterate()
    {
        int i = 0;
        string newInstructions = "";
        while (i < instructions.Length)
        {

            if (instructions[i].ToString() == "A")
            {
                newInstructions += custumisation.rule;//A --> A[AA]
            }
            else if (instructions[i].ToString() == "B")
            {
                newInstructions += "B[A]";//add berry and a branch
            }
            else   // pass what is in there already
            {
                newInstructions += instructions[i].ToString();
            }
            i++;
        }
        instructions = newInstructions;
        custumisation.output = instructions;
    }



    void Update()
    {

  

         if (Input.GetKeyDown(KeyCode.Space)) {
             SceneManager.LoadScene(0);
         }

        if (index < instructions.Length)
        {
            currentLetter = instructions[index].ToString();
            index++;

            //rules
            if (currentLetter == "A") {
                
                currentBranch =Instantiate(branch, positions[positions.Count-1], Quaternion.identity);
                currentBranch.transform.eulerAngles = new Vector3(Random.Range(-60, 60), Random.Range(-60, 60), Random.Range(-60, 60));
                currentBranch.transform.localScale = new Vector3(3, Random.Range(3f,10f), 3);
                currentBranch.GetComponent<SpriteRenderer>().color = custumisation.colours.Evaluate(Random.Range(0f, 1f));
                currentBranch.transform.parent = transform;
            }
            else if (currentLetter == "B")
            {
                GameObject berryRef;
                berryRef = Instantiate(berry, positions[positions.Count - 1], Quaternion.identity);
                berryRef.transform.parent = transform;
                //currentBranch.transform.eulerAngles = new Vector3(Random.Range(-60, 60), Random.Range(-60, 60), Random.Range(-60, 60));
                //currentBranch.transform.localScale = new Vector3(1, Random.Range(1f, 3f), 1);
                //currentBranch.GetComponent<SpriteRenderer>().color = custumisation.colours.Evaluate(Random.Range(0f, 1f));
            }
            else if (currentLetter == "[") { // go up a branch (push)
               positions.Add(currentBranch.transform.Find("top").transform.position);// add to
            }
            else if (currentLetter == "]") { // go down a breanch (pop)
                positions.RemoveAt(positions.Count-1);
            }
        }
        //else index = 0;
    }
}