Thanks @kartofelek007 for that.
I noticed it didn’t affect repeaters with layout set to table, so I added these two lines of css:
.acf-input-table.table-layout .acf-row:nth-of-type(2n) td {
background: #eeeeee;
}
.acf-input-table.table-layout .acf-row:nth-of-type(2n) td.order, .acf-input-table.table-layout .acf-row:nth-of-type(2n) td.remove {
background: #e3e3e3;
}