just: Standardize error messages & make them red in color

[fiftydinar]

Along with making them red in color, we can send those error message to stderror, in case if some just command enabled set -eou pipefail, so the command fails without need to specify exit 1.

I use this format for my just modifications:
echo "ERROR: This is the command which failed!" 1>&2

We can easily specify colors from sourced lib-ujust for this.