=MOD(SUBTOTAL(3,$A$2:$A2),2) is placed in Conditional Formatting in
and column in ROW 2

<<This works even in autofilter

Column A must contain data. If the Cell is filled it is counted. Use
another column if A isnt useful.
$A$2 is start

$A2 is the row you are in A contains the data

Subtotal COUNTS cells filled between $A$2 and $A2

$A2 changes as you COPY it using the Format Painter TOOL