Highlight yanks/pastes on top of syntax highlighting.

Let $zle_highlight[paste] override $region_highlight.

zsh-syntax-highlighting.zsh

@@ -106,6 +106,21 @@ _zsh_highlight()
         region_highlight+=("$start $end $region")
       fi
     }
+    # YANK_ACTIVE is only available in zsh-5.1.1 and newer
+    (( $+YANK_ACTIVE )) && () {
+      if (( YANK_ACTIVE )) ; then
+        # zle_highlight[paste] defaults to 'standout' if unspecified
+        local paste="${${zle_highlight[(r)paste:*]#paste:}:-standout}"
+        integer start end
+        if (( YANK_END > YANK_START )) ; then
+          start=$YANK_START end=$YANK_END
+        else
+          start=$YANK_END end=$YANK_START
+        fi
+        region_highlight+=("$start $end $paste")
+      fi
+    }
+
 
 
   } always {