Why not? If such a curious (ominous?) warning is made in the future, please include just a clue as to why, as this sort of thing can keep me wondering for months! Thanks.
Article Says Don’t Mix Colors in a Pot of Lisianthus
Certified GKH Gardening Expert
Although some resources do mention this, they do not explain why...and most resources for growing Lisianthus flowers say they are fine mixed together, though in containers you may want to stick with the same type as far as height and such. In fact, the dwarf types would be ideal for pots.
Thank you for bringing this to our attention. Our editors have made appropriate changes to make this less confusing.