Tough is related to Strong. Strong is a synonym of Healthy. 
Use is related to Color. Color is related to Pink. Pink is related to Muscle. Muscle is related to Flesh. 
Tough <--RelatedTo--> Strong <--Synonym--> Healthy 
Use <--RelatedTo--> Color <--RelatedTo--> Pink <--RelatedTo--> Muscle <--RelatedTo--> Flesh 