If you just grow white ones, so that even if they cross the pollen is from all white flowers, you will get MOSTLY white flowers from the seeds the next year. But you never know if your neighbor down the street has yellow or orange ones and a stray bee brings pollen from there . . . you'll get all orange ones from that flower the bee pollinated, because the orange trait is dominant.
Seed companies isolate their F1 hybrid plants so they only pollinate with other plants with stable traits. That's how they can be fairly confident to sell you a seed packet of white marigolds, or any other color for that matter.
