not fix yet

Assets/Scripts/BackgroundChanger.cs

@@ -8,7 +8,6 @@ public class BackgroundChanger : MonoBehaviour {
 	private List<GameObject> obstacleGroup = new List<GameObject>();
 	private GameObject[] gameObjectGroup;
 	private GameObject background;
-    private GameObject obstacle;
 	private string[] colors = {"Blue", "Green" };
 
 	public void Start()
@@ -20,21 +19,20 @@ public class BackgroundChanger : MonoBehaviour {
 
 	private void CollectBackgrounds()
 	{
-        foreach(string color in colors)
-        {
-            background = GameObject.FindWithTag(color + "Background");
-            backgroundGroup.Add(background);
-        }
+		background = GameObject.FindWithTag("Background");
 	}
 
 	private void CollectObstacles()
 	{
 		foreach(string color in colors)
 		{
-            obstacle = GameObject.FindWithTag(color + "Obstacle");
+			gameObjectGroup = GameObject.FindGameObjectsWithTag(color + "Obstacle");
+			foreach(GameObject obstacle in gameObjectGroup)
+			{
 				obstacleGroup.Add(obstacle);
 			}
 		}
+	}
 
 	public void Update()
 	{
@@ -49,15 +47,12 @@ public class BackgroundChanger : MonoBehaviour {
 
 	public void UpdateBackgroud(string tagColor)
 	{
-        foreach(GameObject background in backgroundGroup)
-        {
-            if (background.tag == tagColor + "Background")
+		if(tagColor == "Green")
 		{
-                background.SetActive(true);
-            } else
+			background.GetComponent<SpriteRenderer>().color = new Color32(46, 204, 113, 255);
+		} else if (tagColor == "Blue")
 		{
-                background.SetActive(false);
-            }
+			background.GetComponent<SpriteRenderer>().color = new Color32(65, 131, 215, 255);
 		}
 
 		UpdateObstacle(tagColor);
@@ -67,7 +62,7 @@ public class BackgroundChanger : MonoBehaviour {
 	{ 
 		foreach (GameObject obstacle in obstacleGroup)
 		{
-            if(obstacle.tag == tagColor + "Obstacle")
+			if (obstacle.tag == tagColor + "Obstacle")
 			{
 				obstacle.SetActive(false);
 			} else

ProjectSettings/TagManager.asset

@@ -8,6 +8,7 @@ TagManager:
   - GreenBackground
   - BlueObstacle
   - GreenObstacle
+  - Background
   layers:
   - Default
   - TransparentFX

colourful-love.userprefs

 <Properties StartupItem="Assembly-CSharp.csproj">
   <MonoDevelop.Ide.Workspace ActiveConfiguration="Debug" PreferredExecutionTarget="Unity.Instance.Unity Editor" />
-  <MonoDevelop.Ide.Workbench ActiveDocument="Assets\Scripts\PlayerController.cs">
+  <MonoDevelop.Ide.Workbench ActiveDocument="Assets\Scripts\BackgroundChanger.cs">
     <Files>
-      <File FileName="Assets\Scripts\BackgroundChanger.cs" Line="32" Column="2" />
-      <File FileName="Assets\Scripts\PlayerController.cs" Line="14" Column="3" />
+      <File FileName="Assets\Scripts\BackgroundChanger.cs" Line="22" Column="1" />
+      <File FileName="Assets\Scripts\PlayerController.cs" Line="1" Column="1" />
       <File FileName="Assets\Scripts\PhysicObject.cs" Line="1" Column="1" />
       <File FileName="Assets\Scripts\SceneLoader.cs" Line="1" Column="1" />
     </Files>