Purple seen here I am attributing to the cold. Note however that these are the only seedlings showing this degree of purple out of a sea of seedlings both younger and older than the ones shown here. I'm thinking this may be a nice trait to breed for... similar to how Japanese maples through out some beautiful fall colors. If we can breed purples together to create darker purples that while only purple in the cold months...still put out a beautiful show for that short time... to me that would be sweet indeed.
A grafted tray of non-purples for comparison
Food for thought for those interested in further knowledge on this subject.
https://thechillbud.com/20-popular-purple-cannabis-strains/
Update... tonight I'll be bringing these bad boys and girls down to -2 degrees to see if I can get the purple to intensify a bit. Keep those fingers crossed for me.