I just noticed a difference in the blue of the Language Learning Stack Exchange to all other beta Stack Exchange sites I have in my list.
I presume, this is a (minor) design bug, isn't it?
I have visited both links, therefore it should not be a difference between visited and unvisited links in the browser. The browser is Mozilla Firefox 58.0.2 on Ubuntu Linux 16.04 LTS.
EDIT: As of just now, I see in the hot questions list two other beta sites featuring the blue of Language Learning, namely IPS and cse. The following sites currently feature the blue of Open Data: W, PCO, Ph, P, ME, Mv, SX, BG, and RC.
EDIT 2: The small icons occurring in the Top Questions view and in the sidebar hot questions are all of the same blue as the Open Data logo.