When I run open .bash_profile a new terminal opens and
Last login: Wed Nov 30 19:01:22 on ttys004
/Users/MyName/.bash_profile ; exit;
➜ ~ /Users/MyName/.bash_profile ; exit;
[Process completed]
My permissions are
-rwxr-xr-x@ 1 MyName staff 639 Nov 30 19:02 .bash_profile
Also, when I run ls -la, .bash_profile is colored red. I don't know why. It wasn't like that before.
All I was trying to do was create an alias, but now I can't even open my .bash_profile.
tl;dr
To ensure that you open a file in your default text editor using the macOS open CLI, use:
open -t ~/.bash_profile
Otherwise, if the file needn't be excecutable, run chmod -x <file> (chmod -x ~/.bash_profile, in this case) to make open behave like it did before.
From you question I infer that you're on macOS (OS X).
What the macOS open CLI does when passed a file depends on the file's suffix (extension), and, in the absence of one, on whether the file has the executable (r) permissions bit(s) set (if not, the file opens in the standard text editor, which is what you saw before).
A file displaying in red when you use ls -a (the -a being necessary to show hidden items such as .bash_profile), implies that the file is indeed executable by you.
A suffix-less executable (text) file causes open to run it in a new terminal window as a shell script, which is what you're seeing.
In other words: at some point, unbeknownst to you, executable permissions were assigned to ~/.bash_profile, which explains the change in behavior.
However, there is no need for ~/.bash_profile to be executable, because it is sourced by Bash on startup.
As stated above, either remove the executable permissions, or simply use open -t to open it.
