How do I color rows alternately? Not 1 row after the other, but depending on column data

I have some sales data with orders and item details listed in a excel worksheet. The order # is listed in column A, and the items for that order are listed in column B. A single order can contain many items I want all rows in one order to be colored the same, and the next order to be colored differently so that I can see the difference immediately. I've attached an excel sheet to show what I mean! Any help would be appreciated. Thanks!

Select your range

Conditional format


Color 1:

=MOD($A2,2)=0


Color 2:

=MOD($A2,2)=1

You're welcome!