This will enable Konsole to support 256 colors:

1. Open Konsole
2. Right click in the terminal -> Edit Current Profile
3. Find Environment and click Edit.

4. Add the following line:

   TERM=xterm-256color

Now test this by starting a new Konsole tab. Then run:

    mc -S modarin256-thin

If 256 colors are supported, mc will start up in a dark 256 color theme. If it does not work, mc will output a message saying that terminal does not support 256 colors.

This is how mc looks with 256 color support and modarin256-thin theme.