Coloring the Custom Inspector

Hello people, i have a small question. I am not really good at this custom inspector stuff, I am trying to learn some new tricks all the time. Now, I can create a custom editor, basically like this:

 using UnityEngine;
 using System.Collections;
 using UnityEditor;
 
 [CustomEditor(typeof(IE_WeaponScript)), CanEditMultipleObjects]
 public class IE_WeaponScriptEditor : Editor {
 
     
     public override void OnInspectorGUI()
     {
         IE_WeaponScript weaponScript = (IE_WeaponScript)target;
         serializedObject.Update();
 
         // My fields...
 
 
         serializedObject.ApplyModifiedProperties();
     }
 }

I simply want to color the inspector, instead of default light grey, I want to color it to red, or black anything. I searched it up, found this. But could not apply it to my needs, i think that is about CustomWindows. So, is there any little trick that does this or do I have to draw a texture behind all my elements in the custom inspector, if so, how can I draw it properly in order to make it cover all the inspector? Thanks :).