This issue was introduced with the fix for the issue
MDL-37845. Please refer to it for additional information.
Preequisite: MathJax should be installed and enabled.
Steps to reproduce:
1. Create a test in a course with answer mode "Show immediate feedback"
2. Create a question with feedback which contains Latex
3. Answer the question. Feedback is now shown but the colors are all wrong. Please refer to the following screencaps http://imgur.com/B48v5kh,ItmN0GN.
The fix is pretty easy and can be found at git://126.96.36.199/moodle/moodle.git in branch