I want to make the console foreground color "green".

(Note: I can't make this clearer, it seems every time I say "console" people assume something like XTerm/Konsole/Gnome-Terminal/ETerm/ATerm/etc. Nope. That's not what I'm refering to. I'm talking about the "no X" console. ttyv1, ttyv2, etc.)

Setting PS1 is not what I'm looking for [it won't even do the job].

I want the "default" console color to be "green" instead of "grey" [or whatever] [boot messages should also appear in this color].

I do not use a frame buffer.

I am willing to "fix" this by modifying some kernel source files. [Any hints on what files I should look into?]

I only run Slackware here, but on a firewall box here, I changed a line in /etc/rc.d/rc.M to

/bin/setterm -blank 0 -foreground green -background black -powersave powerdown -powerdown 60

This causes the terminal display to have green text on a black background.

The foreground and background can be changed to what you want within limits.

Hope this is close to what you are looking for.

Will temporarily set the color to green. Calling VIM (or screen, or whatever) will turn the text back to Grey. Thus, setterm doesn't really work.

I would use a framebuffer but I've heard they can be pretty slow [slower than X terminal emulators].

I don't think we can be sure about that. Don't you know that the framebuffer and its drivers is especially created for text? Perhaps it will just depend on the driver you're using.