I apologize for the lack of hinting. There are actually more.
If you haven't also found a green door, then you haven't break boxes in the big area yet. The area that has a lot of tables, there are stairs on the left.
Viewing post in Metal Pipe Freaks jam comments
I definitely did find green doors, I couldn't have gotten to the red keycard otherwise lol.
I had no idea that the player could break boxes after getting the pipe... that's a pretty big backtrack to have to find that out, basically back to the very start of the game. It would have been good if there were boxes in front of Bean that the player had to break to get to her - that way, after you get the red keycard, you know to search for boxes to find where the red doors should be.