Get a white texture.

	// Load a texture, display the texture, display its alpha channel and
	// show a preview of the inverted texture
	
	class EditorGUITextures extends EditorWindow {
	
		var texture : Texture2D;
		var invertedTexture : Texture2D;
		var showInverted = false;
		
		@MenuItem("Examples/Texture Previewer")
		static function Init() {
			var window = GetWindow(EditorGUITextures);
			window.position = Rect(0,0,400, 200);
			window.Show();
		}
		
		function OnGUI() {
			texture = EditorGUI.ObjectField(Rect(3,3,200,20),
					"Add a Texture:",
					texture,
					Texture);
			if(GUI.Button(Rect(208,3, position.width - 210, 20),"Process Inverted")) {
				if(invertedTexture)
					DestroyImmediate(invertedTexture);
				//Copy the new texture
				invertedTexture = new Texture2D(texture.width, 
						texture.height, 
						texture.format, 
						(texture.mipmapCount != 0));
				for (var m : int  = 0; m < texture.mipmapCount; m++) 
					invertedTexture.SetPixels(texture.GetPixels(m), m);
				InvertColors();
				showInverted = true;
			}
			if(texture) {
				EditorGUI.PrefixLabel(Rect(25,45,100,15),0,GUIContent("Preview:"));
				EditorGUI.DrawPreviewTexture(Rect(25,60,100,100),texture);
				EditorGUI.PrefixLabel(Rect(150,45,100,15),0,GUIContent("Alpha:"));
				EditorGUI.DrawTextureAlpha(Rect(150,60,100,100),texture);
				EditorGUI.PrefixLabel(Rect(275,45,100,15),0,GUIContent("Inverted:"));
				if(showInverted)
					EditorGUI.DrawPreviewTexture(Rect(275,60,100,100),invertedTexture);
				if(GUI.Button(Rect(3,position.height - 25, position.width-6,20),"Clear texture")) {
					texture = EditorGUIUtility.whiteTexture;
					showInverted = false;
				}
			} else {
				EditorGUI.PrefixLabel(
					Rect(3,position.height - 25,position.width - 6, 20),
					0,
					GUIContent("No texture found"));
			}
		}
		
		function InvertColors() { 
			for (var m : int  = 0; m < invertedTexture.mipmapCount; m++) {
				var c : Color[] = invertedTexture.GetPixels(m);
				for (var i : int = 0 ;i < c.Length; i++) {
					c[i].r = 1 - c[i].r;
					c[i].g = 1 - c[i].g;
					c[i].b = 1 - c[i].b;
				}
				invertedTexture.SetPixels(c, m); 
			}
			invertedTexture.Apply();
		}
		function OnInspectorUpdate() {
			Repaint();
		}
	}