i believe there is another solution for your problem, add column E=if (d2=0,Today()-B2,0)
and let the format of the column be number
in this case you will get the number of days since start date till today and the conditional format could be done on this column E
if cell E2 between 1 and 14; format Color Orange
if cell E2 between 15 and 21; format Color Red
then if it was zero the format won’t be affected.
Hoping i was able to help