diff: restore original color scheme for worddiff

I'm not young. "red dim" is nearly invisible, and "red" vs "red dim" is
too subtle to see difference. And, "underline" is necessary to highlight
whitespace changes.

mercurial/color.py

@@ -90,16 +90,16 b' except ImportError:'
     'branches.inactive': 'none',
     'diff.changed': 'white',
     'diff.deleted': 'red',
-    'diff.deleted.changed': 'red',
-    'diff.deleted.unchanged': 'red dim',
+    'diff.deleted.changed': 'red bold underline',
+    'diff.deleted.unchanged': 'red',
     'diff.diffline': 'bold',
     'diff.extended': 'cyan bold',
     'diff.file_a': 'red bold',
     'diff.file_b': 'green bold',
     'diff.hunk': 'magenta',
     'diff.inserted': 'green',
-    'diff.inserted.changed': 'green',
-    'diff.inserted.unchanged': 'green dim',
+    'diff.inserted.changed': 'green bold underline',
+    'diff.inserted.unchanged': 'green',
     'diff.tab': '',
     'diff.trailingwhitespace': 'bold red_background',
     'changeset.public': '',