I noticed this problem when customizing for UI color.
How to recreate it?
It cause on WindowsOS & MacOS.
See the list of color item a following.
Preferences : General:
I checked this on Wings3D v2.1.7(Mac) & v2.2.1(Win)
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Best Regards 
	
	
	
	
How to recreate it?
Preferences : User interface > turn on "Use Native color dialog" checkbox.
To edit the color to click a color cell .
In some color editing, Wings color dialog appears instead of native color dialog.
(Perhaps, the program invoked the wings color dialog alternatively.)To edit the color to click a color cell .
In some color editing, Wings color dialog appears instead of native color dialog.
It cause on WindowsOS & MacOS.
See the list of color item a following.
Preferences : General:
- vertex display > magnet mask color
 
- information text> background color
 
- window background color
 
- Magnet radius display color
 
- Background color 
 
- *Custom Pattern* (Hexagon,Marble patterns etc...)
 
I checked this on Wings3D v2.1.7(Mac) & v2.2.1(Win)
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Best Regards
 
	 
	 
