I'm asking this from the perspective of the TeX-SX site. Basically, we don't want them unless they are really questions about TeX and not about MathJaX. In particular, questions about configuring MathJaX, about installing MathJaX, and about how to do something particular in MathJaX, are all off-topic on TeX-SX. The reason being that MathJaX does not use TeX and so expertise in TeX does not help at all in answering questions such as those above. Although we have a MathJaX tag, the phrasing hopefully makes this clear: http://tex.stackexchange.com/tags/mathjax/info
To be absolutely clear, it isn't that we have anything against MathJaX. It is because the expertise that exists on TeX-SX has no relevance whatsoever for helping people with MathJaX and therefore it is in the questioner's best interests to find a better place to ask their question.
But we occasionally get questions about it, and also get questions migrated from other sites about it. Where should we redirect those questions on this network, if anywhere? Our tag, linked above, suggests the main StackOverflow site, but the most recent migration (and the reason why I'm asking this) came from there. And was migrated after it had been answered by the lead developer of MathJaX!
StackOverflow version: MathJax and LaTeX \definecolor