Alternating color in visible rows based on column value in Excel

This is similar to Alteate grid background color in excel when a value of a single column changes? , and I believe it can be done using SUBTOTAL(109,... , but I can't quite figure it out.

The first column in my table is a group number, and all rows with the same group number should have the same background. The table is sorted by the group number.

I want to alteate the row color per group, based only on the visible rows. In this example I've hidden A and C . Note that praesent and libero have swapped colors based on the visible rows.

I'm free to add in hidden helper formula columns, but I'd prefer it all to be in the conditional formatting.

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