Select from A4 to D7 and try these conditional formatting formulas:

=AND($F4<>"Paid",TODAY()-DATE(YEAR(TODAY()),MONTH(TODAY()),$E4)>=6) for orange

=AND($F4<>"Paid",TODAY()-DATE(YEAR(TODAY()),MONTH(TODAY()),$E4)>=3) for blue

=AND($F4<>"Paid",TODAY()-DATE(YEAR(TODAY()),MONTH(TODAY()),$E4)>0) for green

in that order