feature request: showing known topics with slightly different color

[sygi]

One thing I miss in metacademy is that all the concepts links have the same color. I would like to have a possibility to see a page of only unknown concepts or to distinguish between known and unknown with a slightly different color (e.g. lighter violet for known topics).

I wanted to do it myself and send you a pull request, but I need a bit of help.
I wanted to add an extra class for the known topics in this function:
https://github.com/metacademy/metacademy-application/blob/master/server/apps/roadmaps/views.py#L59
but it is executed as a callback, being distant from the request, from which I could get a list of known topics. I also saw that in some places you put the known topics into javascript code and do stuff from there, but I did not manage to find a place in code to do that.

1. do you think that this feature makes sense?
2. would you give me a hint about way of implementing this?
   Thanks