I have an Excel list where the first column identifies a group, like
1
1
1
3
4
4
6
6
6
Now I want to color the rows of the groups alternating for better readability.
Group 1 (the rows starting with 1) - red
Group 2 (the rows starting with 3) - blue
Group 3 (the rows starting with 4) - red
Group 4 (the rows starting with 6) - blue
....and so on

The numbers in this list are not in sequence and have gaps.
The number of rows belonging to a group differs from group to group.

Any smart and experienced guy out there who can help?