I think the mix for Skimmers in the colder months should stay the same as in the warmer months.
The important part is the loose feed content and the amount of stuff you put into your swim, like ranging from just a few casters and squats too nill loose feed,and then only through the open ended feeder
aswell as being spot on ever cast with the feeder,that meens using the line clip ever cast in order to keep the small amount of feed that does go into your swim in a tight an area as possible.
Sensus 3000 Bream is the stuff I use most, but VDE supercup takes some beating,both come in brown or red.
This is an endless topic especialy when you start talking of chopped worm aswell crushed caster juice.