IF statement on a df -g

Im running reports on a unix box.
i run df -g and get the disk usage results, what i want to do is hopefully run an if statement or of the sort to highlight any percentages over 80 %.

I also would like to run an errpt and also highlight any errors for the current days date.

Could the results be highlighted in a different color, or could i just get only disk space over 80% to be listed and errors only for current date displayed.

Many thanks

why not try :

df -k | awk '{ if ($5 > 80 ) {print $0 } }'