Access Variable through script // SerializedField (C#)

Hey guys, I want to adjust the Tonemapping Color Grading parameters through a script when I enter a trigger. However I can’t manage to access the “colorGrading” Variable in the original script. Could this be due to the “SerializeField”? Thanks for your help!

 namespace UnityStandardAssets.CinematicEffects
    {
        using UnityEngine;
        using UnityEngine.Events;
        using System;
    
        [ExecuteInEditMode]
        [RequireComponent(typeof(Camera))]
        [AddComponentMenu("Image Effects/Cinematic/Tonemapping and Color Grading")]
        public class TonemappingColorGrading : MonoBehaviour
        {
    #if UNITY_EDITOR
    
    [....]
    
    
            [SerializeField, SettingsGroup]
            private ColorGradingSettings m_ColorGrading = ColorGradingSettings.defaultSettings;
            public ColorGradingSettings colorGrading
            {
                get { return m_ColorGrading; }
                set
                {
                    m_ColorGrading = value;
                    SetDirty();
                }
            }

any chance resolving this issue?