Any cut, injury, or bruise turns red. There are diseases that also result in "red", but likely your red is the result of cutting. Did you dust the cut plate prior to planting?
K

I didn't have any Captan, so I let the plate dry and then set it on the soil without burying it. I was afraid to use cinnamin on the basal plate since it reportedly affects rooting. I do have Captan arriving today or tomorrow, soI can dust it then, if it isn't too late.

I bet it will be ok. We get startled by red, but in some cases it's fine.
K

I can't recall if there were any red visible post cutting on my "Emerald" pieces... but hopefully, as Kristi said, it will be fine... time will tell.

Here are some examples of red that might startle you, but they are ok. Cut neck and leaves as things were being moved into the greenhouse. Those leaves will turn yellow and limp and I'll trim down each bulb leaving a nice open neck. I usually dust liberally with Captan powder. This one got missed.
K