Got it- thanks for the file, that helped tremendously. I got the
results you're looking for by doing this:

1. Insert new columns B and C.
2. For each driver, populate the days of in B and C using integer
numbers, where 1=Sunday, 2=Monday, etc thru 7=Saturday. In the sample
data, the first three rows look like this:
....A.........B....C
Driver 1....7....1
Driver 2....1....2
Driver 3....4....5

3. Create conditional formatting for cell D1 (that cell is now Day 1
for Driver 1) with this formula:
=OR(WEEKDAY(D$3)=$B4,WEEKDAY(D$3)=$C4)
....and apply the format you desire. Copy that cell and paste it for
the rest of the days in the month and the rest of the drivers.

Let us know how it goes!
Dave O