Paint is related to Colorful. Colorful is the opposite of Gray. Gray is related to Shade. Shade is a synonym of Shadow. 
Mystery is related to Spy. Spy is a synonym of Sight. Sight is related to Fog. 
Paint <--RelatedTo--> Colorful <--Antonym--> Gray <--RelatedTo--> Shade <--Synonym--> Shadow 
Mystery <--RelatedTo--> Spy <--Synonym--> Sight <--RelatedTo--> Fog 