Protip: Never use a light grey to outline any tiles as it looks bad. That outline is used for NPCs. Instead, use the color that was used for the outline for the SMB1 Tree BGOs
Here's a little "patch" for those who find the light gray outline of the blue door a little off.
Right click the graphic and click "Save (image) as". You must replace the underscore (_) with the hyphen-minus (-) in "background_105.gif" when you're saving it and it must be in the SMB1-Recolored SMW Ghost House folder.