tasks #6730: Use white/black color for xref-in-title

Change-Id: I6bb9dfaed24fd93115c609a6dd5bff3e692cc1b8
Merge commit 'refs/changes/16/2316/4' of http://gerrit.tuleap.net/tuleap into HEAD

* http://gerrit.tuleap.net/tuleap:
  tasks #6730: Use white/black color for xref-in-title

Change-Id: Ib7e7276c546ff468bd71118bdcbcf53004a69093
This is Tuleap 6.12.99.65

Change-Id: Ie7171125defb8358a48ae43c1a784804d12eea77