Referencing different cells in order to condionally format another

Just leave cell L1 as is.

For column E, use this formula in the conditional format:

=WEEKDAY($L$1,2)=1

For column F, use this formula in the conditional format:

=WEEKDAY($L$1,2)=2

For column G, use this formula in the conditional format:

=WEEKDAY($L$1,2)=3

For column H, use this formula in the conditional format:

=WEEKDAY($L$1,2)=4

For column I, use this formula in the conditional format:

=WEEKDAY($L$1,2)=5

Cheers,