Bonjour, Anna lisa.

I only know of two ways that a lily can "change" colours.

1) Some lily colours (especially dark ones) gradually fade as the flowers get older. They open darker, but become lighter within a few days. Some of these lilies do not fade as much if they are planted in a little bit of shade.

2) A lily could be pollenated by a lily of a different colour and form a viable seed. If this seed falls from the plant and germinates, the flower might be a different colour from the mother plant. But, because the two plants are so close together, it could appear as though the mother is changing colour (especially if, for some unrelated reason, the mother plant dies).

I have grown lilies for many years, and none of them have changed colour (except for reason #1). Enjoy your new plants. The pink and white one sounds especially lovely. Don't worry...it won't turn into any other colour.

'Lilium' is the botanical name of all 'true' lilies. (Daylilies are NOT 'true' lilies.) Liliums don't change color---no need to worry.