How to print both matched and non matched lines?

[Peng Yu]

Hi,

I use --color=auto, so that I can distinguish nonmatched lines from
matched lines by looking at the colored text if the non matched lines
is shown. But I don't see an option to allow me show all lines. Would
you please let me know if there is such an option if I miss anything
in the man page?

-- 
Regards,
Peng