Took a look at it in Panel View
The TilePicker has one Panel which is a parent of the grid which contains the tile images that are bleeding through.
It has a depth of 1. The images have a depth of 3.
All of the Script editor depths are 20 or greater, including all the panels.
This really seems to be a result of those images having been added to the tile picker in code. If you are curious, here is the code that adds them:
UIGrid grid = GetComponent<UIGrid>();
UIWidget widget = transform.parent.GetComponent<UIWidget>();
foreach(TileRecord rec in tileRecords){
GameObject panel
= new GameObject
(); UITexture nguiTexture = panel.AddComponent<UITexture>();
nguiTexture.mainTexture = rec.tilePreviewImage;
nguiTexture.depth = widget.depth+1;
nguiTexture
.transform.localScale = new Vector3
(0
.5f,0
.5f,
1); panel.transform.parent = transform;
panel.transform.localPosition = Vector3.zero;
nguiTexture.MarkAsChanged();
NGUITools.AddWidgetCollider(panel);
UIDragScrollView dsv = panel.AddComponent<UIDragScrollView>();
dsv.scrollView = grid.transform.parent.GetComponent<UIScrollView>();
TileClickManager tcm = panel.AddComponent<TileClickManager>();
tcm.tileRec = rec;
tcm.mapCursor = cursor;
}
grid.Reposition();
transform.parent.GetComponent<UIWidget>().MarkAsChanged();