Update topBar-buttons.md (#3348)

docs/docs/topBar-buttons.md

@@ -12,7 +12,7 @@ The following options can be used to customise buttons.
   title: 'Button one',
   enabled: true,
   disableIconTint: false,
-  tintColor: 'red',
+  color: 'red',
   disabledColor: 'black',
   testID: 'buttonOneTestID'
 }
@@ -87,4 +87,4 @@ Navigation.mergeOptions(this.props.componentId, {
     rightButtons: []
   }
 });
-```
+```