I got it figured out now. I made it like this:
.columns-2 .pricing-table-column {
width: 30%;
}
.pricing-table-column.label-column {
width: 40%;
}
.columns-3 .pricing-table-column {
width: 30%;
}
.pricing-table-column.label-column {
width: 40%;
}
I have put it in de Custom CSS in the Suptreme Theme > General options > Custom CSS
Thanks!