My first winter growing trich seedlings saw alot of purples and pinks. My observations were that Lophs particularly like to purple and the younger the seedlings are the more likely as well. As the nights are warming up green has returned to most. Some have started to pup green whilst the wintered section remains purple (rather than reverting back to green as a whole).
Would the reason be that the cold has affected the tissue so, that there has been some cell death?