Sum of coloured cells by date

[christan89]

I am putting together a system for end of shift reporting and I am trying to add the total downtime per shift.
Each shift has a set colour and i am able to add the total value to each colour but the end of shift reporting is based over a week so is there a way of add the values of a set colour over a set date? i.e.
Blue cells on the 01/01/2012, blue cells on the 02/01/2012
Green cells on the 01/01/2012, green cells on the 02/01/20212