LinuxQuestions.org - display colour values for terminal supported colours

I have been trying to customise urxvt's colour scheme in ~/.Xresources. I have been struggling with one of the colours (ie. #ad7fa8). It won't get displayed. I figured out that it must be unsupported as by default urxvt supports only 88 colours. It's not a big problem as I used this little piece of code to display supported colours in urxvt:

Code:

(x=`tput op` y=`printf %80s`;for i in {0..256};do o=00$i;echo -e ${o:${#o}-3:3} `tput setaf $i;tput setab $i`${y// /=}$x;done)

The only way of getting the colour values I can think of would be to take a screenshot of the output, open it in gimp and sample particular colours. Is there a way to automatically display the values in the terminal (eg. possibly to modify the above snippet)?

Thank you.

edit: I am aware of the patch to enable 256 colours in urxvt. It is AN option, but I don't think I need 256 colours:) I'll make do with the ones that are supported by default.