Even indoors you have the chance of self-pollination, so people are cutting the stamen of the flowers they want to produce crossed seeds with. Also you can't be sure that your plants will be pollinated. Perhaps someone else can answer you how your chances in succeeding that way are.

If you want to make sure that you have seeds that are the results of different parents, especially if you want to know which parents produced which colour, pollinate them yourself.

Chances are good if the flowers are next to each other and they are blooming at the same time..some insect or even the wind will take care of it. But to be sure, do as betonklotz above has suggested..pollenate them yourself! It's so simple..just use your finger..and Good Luck..

Donna