How to use `docker compose exec` with both grep and ANSI color?

Question

I'm only casually familiar with Docker, and how TTYs work in Linux. At work, I use commands like docker compose up to start the development stack (Postgres + Django), and docker compose exec web python manage.py ... to run Django commands during development.

Conflicting problems:

1. I can't pipe in input or grep output without adding -T. I don't know why, I just know it works with it, and not without it.

   • I populate the DB with docker compose exec -T db psql -U username myproj < snapshot.sql because without the -T the input doesn't make it to psql.
   • I also add -T when I have to grep the output, like:
     docker compose exec web python manage.py showmigrations | grep '[ ]'.

2. However, when I use -T, it screws up ANSI coloring and formatting.

   • Without -T:
   • With -T:

Question: What's the correct method? How do I properly connect STDIN & STDOUT without messing up color & formatting?