For the purposes of collaboration, I want to create a number of short commands or environments that will color the text within its scope so as to identify the author.

My first thought was to simply create a number of new commands along the lines of the suggestions given here. But I'm imagining that the various collaborators would be writing several pages of text at a time and I don't know whether large blocks of text (and perhaps multiple new environments within that text) brings with it issues that would decide in favor of using new commands or environments.

Is there a reason to choose one or another route to coloring large blocks of text?

In general, when is it better to use a new command vs. a new environment (if there is any substantial difference)?

UPDATE: Well I think I've come up with a partial answer: making commands following the model given in the linked answer (\newcommand{\red}[1]{\textcolor{red}{#1}}) won't allow you to place multiple paragraphs within the scope of one command instance. Each paragraph requires a new instance of the coloring command (unless I'm doing something wrong). This would seem to be one reason to go the environment route.

FURTHER UPDATE: It turns out that the limitation of the command approach was a limitation of \textcolor, not some general limitation on new commands. Using \color allows you to color multiple paragraphs.