Anyone knows if it's possible to color command line commands as you type them (kind of like an editor)?

I suggest trying this one for Zsh, over the more common one: https://github.com/zdharma-continuum/fast-syntax-highlighting

If you use zsh, there is zsh syntax highlighting plugin. For bash, a cursory search gave me ble.sh which looks interesting. And as other threads have mentioned, fish shell has this built in, but beware fish shell syntax works drastically differently from other POSIX shells

beware fish shell syntax works drastically differently from other POSIX shells

Come on, that's scaremongering :)

On interactive, day-to-day use, fish syntax is basically the same as bash or any other shell: you type your commands, hit enter and the command is run. Only when it comes to scripting (or writing complex one-liners, or copy-pasting stuff from the web) are there appreciable differences. In those cases, until one is accustomed to fish, running the command/script in bash is still an option.

Let me be 100% clear: yes, fish will complain if a wildcard doesn't expand to anything, and there are other minor things that may impact typical interactive use. I'm just saying there is basically zero learning curve if you want to try fish and that you can just fire up bash if you hit a wall in a moment when you can't afford to investigate because you need stuff done.

If I had to say, the most hassle with fish is that people assume you are running POSIX shell and so you have to know how to adapt instructions to your shell. For example, someone may say "add expor SOME_VAR=some_value to your .bashrc" and you need to be able to translate that to fish. Also, there is very specific software (in my system, it's just sdkman, an utility that manages which java development tools are installed/available in a shell session) that only works in POSIX shells and needs some adapter for fish.
- Having to adapt to shells is exactly why I don't like to use radical shells like fish or nushell. I don't want to feel too comfortable with them, because if I do, I would probably regret it when I'm stuck in situations that doesn't have the correct shell. SSH into a new server or Raspberry Pi that has DNS issue, for example, which actually happened to me more than once. The DNS is already troublesome, and I don't want shell unfamiliarity to become another headache
I'll be honest, I use bash and the only benefit using ble.sh has over zsh, is that vi(m) mode is better than zsh. For example, more complex commands like di" (delete inside ") don't work in zsh, but work in bash with ble.sh. Also, I found ble.sh far more complicated and took me a while to get it configured. Even now, some completions, especially tab completion, isn't as good in bash as in zsh. In fact, the only issues I had with zsh compared to ble.sh were vi mode related. More specifically, the aforementioned lack of advanced vi(m) mode commands, and the limited support for showing the current vi mode in the prompt, for example for Visual mode (Normal and Insert mode seem to be the only ones to work).

So if you need advanced vi(m) mode, get ble.sh configured. Otherwise, go for zsh.

adjust the knobs on your terminal until the shade of green or yellow is pleasing

What you are looking for is called Syntax Highlight. Are you asking this for the terminal? I think this is a property of the shell. Fish has it builtin and for ZSH, there is a plugin: https://github.com/zsh-users/zsh-syntax-highlighting I don't know if its possible with Bash.

Closest thing for bash would be ble.sh.
- Tried it out and it works! Thanks!
- Yeah, I used to use that before. But its slower for me. So now I use fish for interactions
Yes, I am looking for a syntax highlighter for the terminal. The one I use is called Kitty.
- It would make sense for the terminal to handle syntax highlighting since that would match how editors work. But the convention is that the shell handles highlighting, not the terminal. You can check which shell you are running with the command,
  
  $ echo $SHELL
  
  It's done that way because the shell is a running program that is capable of telling the terminal which colors to show (by mixing color escape sequences into text). Compare that to code in an editor which is text, not a running program so the only option is for the editor to handle highlighting[1]. Editors need syntax files to configure highlighting for all the different programming languages, while terminals don't need this because the shell tells them what colors to show.
  
  [1] setting aside the "semantic highlighting" LSP capability - that was invented long after syntax highlighting conventions were established

Fish shell

You can change the used shell in the configs. At least for Alacritty, when I used it (dont care, it was still kinda broken, I just use Konsole)

Interesting, I never heard of setting your shell in the emulator config. I just used 'chsh' once when I setup the install.
- Yeah please dont use chsh.
  
  Zsh may work, dash (which is a faster, smaller reimplementation of bash) may work.
  
  But fish absolutely doesnt.
  
  Just because you want to have a nice writing experience, that doesnt mean your whole OS needs a different shell.
  
  I will experiment with dash though. Ubuntu uses it as the root shell, so it is really well tested.

Fish

Powershell does this on Windows. May also work on Linux?

I think there's a zsh script that does this as well but I can't remember the name of it.

Powershell does this on Windows. May also work on Linux?

Yes: https://learn.microsoft.com/en-us/powershell/scripting/install/installing-powershell-on-linux

Should you choose to install it, it will bring the total of people running powershell on linux to one :)

(I'm kidding, of course, more or less)
- Powershell may have a stupid syntax, but it's actually pretty good if you look beyond that. Piping objects between scriptlets is so much better than the awk/grep workflows on Linux.
  
  I tried to use it as a base scripting language for a while but I just can't get over the super verbose command line. Probably great for scripts, but not great in an interactive terminal.
zsh-syntax-highlighting

There's also a fork called fast-syntax-highlighting, I use it.