fix [29045] (.default, not .default2), re #3767

git-svn-id: svn://develop.studip.de/studip/trunk@29059 c5b85792-5220-0410-ad23-ed5b6b8ad999
refine [29059] by adding a transition when changing the background color, re #3767

git-svn-id: svn://develop.studip.de/studip/trunk@29061 c5b85792-5220-0410-ad23-ed5b6b8ad999