How to publish colour change to all objects that have script attached in the editor without pressing play?

Hello all,

I'm working on a 2D game in which you play one day of each season. At the end of the year the cycle repeats. There is a unique colour palette for each season.

I would like to create a tool for the artist I'm working with so they can choose a colour for each sprite in each of the seasons. They should be able to select a season from a drop down menu, and all other sprites with this script attached should reflect that change by showing the appropriate colour for the season so they can work in context.

I feel like I'm close, but I've been struggling with that last part for ages now. Currently I have a script set up called ColourPaletteTool with a custom editor that is multi-object editing enabled using scriptableObjects. When I select multiple objects and change a colour, that change is reflected for all objects selected. Likewise when I change the season, all selected objects change to the appropriate colour. However, no other object update until I click on them and reveal the script in the inspector.

I've tried using events, but had no luck, though I feel that this is the answer. I'm using OnInspectorGUI() at the minute which gets called far too often (and doesn't achieve the desired effect), and I only need to publish this change once when a new season is selected.

Here is what I have so far. Any pointers would be greatly appreciated.

 // Custom editor 
 [CustomEditor(typeof(_ColourPaletteTool)), CanEditMultipleObjects]
 public class _ColourPaletteToolEditor : Editor
 {
     // Set up the serialized properties
     SerializedProperty winter;
     SerializedProperty spring;
     SerializedProperty summer;
     SerializedProperty autumn;
     SerializedProperty currentSeason;
 
     void OnEnable()
     {
         winter = serializedObject.FindProperty("colourPalette.Array.data[0]");
         spring = serializedObject.FindProperty("colourPalette.Array.data[1]");
         summer = serializedObject.FindProperty("colourPalette.Array.data[2]");
         autumn = serializedObject.FindProperty("colourPalette.Array.data[3]");
         currentSeason = serializedObject.FindProperty("currentSeason");
     }
 
     public override void OnInspectorGUI()
     {
         // Update the serializedProperty - always do this in the beginning of OnInspectorGUI.
         serializedObject.Update();
 
         // Show the custom GUI controls.
         SeasonManager.SelectSeason((Season)EditorGUILayout.EnumPopup("Season", SeasonManager.CurrentSeason));
         currentSeason.intValue = SeasonManager.CurrentSeason.GetHashCode();
 
         winter.colorValue = EditorGUILayout.ColorField("Winter", winter.colorValue);
         spring.colorValue = EditorGUILayout.ColorField("Spring", spring.colorValue);
         summer.colorValue = EditorGUILayout.ColorField("Summer", summer.colorValue);
         autumn.colorValue = EditorGUILayout.ColorField("Autumn", autumn.colorValue);
 
         // Apply changes to the serializedProperty - always do this in the end of OnInspectorGUI.
         serializedObject.ApplyModifiedProperties();
     }
 }
 
 //  Season manage (one instance of this class)
 [ExecuteInEditMode]
 public class SeasonManager : MonoBehaviour
 {
     public static Season CurrentSeason = Season.Winter;
     public static _ColourPaletteTool[] tools;
 
     public static void SelectSeason(Season season)
     {
         CurrentSeason = season;
         tools = (_ColourPaletteTool[])FindObjectsOfType(typeof(_ColourPaletteTool));
         foreach (var tool in tools)
         {
             tool.UpdateColour();
         }
     }
 }
 
 // Tool script (many instances of this class)
 [ExecuteInEditMode]
 public class _ColourPaletteTool : MonoBehaviour
 {
     [SerializeField]
     private Color[] colourPalette = new Color[4];
 
     [SerializeField]
     private int currentSeason = SeasonManager.CurrentSeason.GetHashCode();
 
     void OnValidate()
     {
         UpdateColour();
     }
 
     public void UpdateColour()
     {
         GetComponent<SpriteRenderer>().color = colourPalette[currentSeason];
     }
 }