Code:
program:
arguments(date, colourA, colourB, colourC);
now = format_date(today(), 'yyyy-MM-dd');
if days_between(now,date) <#1 then colourA
elif days_between(now,date) <=#7 then colourB
elif days_between(now,date) <=#30 then colourC
fi
A shortcut template I use for column colouring, like such:
colours_daysbetween($#lastread, '#00aaff', '#69cfff', '#9bdeff')