[Enhancement] Allow a user to choose a highlight color other than yellow

[gwtaylor]

I'm annotating a textbook that already uses yellow highlighting. Therefore it would be nice to to change the default color of annotations, both on a per-annotation basis but also at a global level (perhaps in user profile).

[JumanaFM]

Great idea! As a hack, there is a feature that we have added on NB2 in which instructors can "spotlight" comments by changing their colors. Currently, the default color is green but we are planning to give users the option to change the colors.

[gwtaylor]

Thanks! This is definitely a great workaround in areas that are already heavily yellow-highlighted in the text itself.