Add in Color Differentiation for Group v. Individual Tasks

[xehu]

In pilots, I encountered a problem where participants seemed to think that being in an individual task was a mistake. In fact, they would send me emails, saying "no one else is in my room," even though that was supposed to be the point of the task.

This is a very small PR that only affects the Morality experiment. (It only impacts cases that have dynamicTeamSize = true).

The purpose of this PR is to address the above issue by adding color-scaffolding for individual versus group tasks.

So, a group task will look magneta, like this:

And an individual task will look green, like this:

The code is slightly hacky, because I basically figured out how to change the underlying CSS by inspecting the rounds and doing a little bit of trial and error. However, I tested it repeatedly and it seems to work as expected. If there are any style changes that would make this better, please let me know.

[xehu]

Merging in color differentiation for morality.