These beans do not need to be cross pollinated, they are both of the type phaseolus vulgaris. They pollinate themselves, even before the blossoms open. You get beans from both varieties without any bees or other insects pollinating and you don't need two varieties for pollination.

I get where you are going with this question:

If you want to try a deliberate cross, all you need are two flowers at the same time. Beans do not flower all at once but over time, so there could well be enough overlap. Easier if you had more than one plant each of course.

Thank you Galina.