No, you don't need to worry. If cross pollination were to occur, it would only mean that any future plants grown from their seed might not resemble the plant you gathered the seed from. The colors/flowers of the parent plants won't change so feel free to plant contrasting and complimentary colors.

If you aren't planning to attempt growing from seed, hopefully you are deadheading spent flower trusses so no seed is set. Producing seed takes a considerable amount of plant energy that would otherwise be directed to the formation of flower buds for the next Spring and a prettier show in your garden.

THANKS!

I am not planning to collect seeds, I trim off the spent blossoms.

Actually, the new white one is loaded with closed blossoms. Should i leave them on when I plant?

Absolutely leave them on and enjoy the flowers when they open.