<p>I use the dark-blue2 color theme but it seems ugly under console.
So I want to use no color theme under terminal, what can I do then?</p>

Set a "TERM" variable corresponding to a monochrome terminal before launching Emacs. For example, if you are in an xterm, use:
```
```
TERM=xterm-mono emacs -nw
```
```
If by "console" you mean the Linux console in text mode, you can try using "vt100" (or "vt320") instead.