I'm only talking still waters here, but on the waters I fish (for roach) reds are definitely the most productive bait and these fished 'handle bar' fashion. Best is a single on a 22 in winter although not so fussy in the warmer months. I take both red and white every time I go as contrary to what I've written above, and for no apparent reason, a change to a singe white brings results and even with fish feeding well on them a quick change back to a red fails to produce anything! Just to make it even more frustrating the fish can change to the other the next day...
On the odd occasion I can catch the odd couple of fish on one of each, so if I'm struggling I will chop and change, even going to an 18 with two of one and one or the other, just as an experiment, which sometimes produces the odd half decent perch. I'm all for experimenting with all sort of combinations, particularly in cold weather, but for my money presentation is probably the most telling factor (along with the freshest of bait) so varying the depth and shotting just as critical in my book.
I see little point in making the effort to go out in the cold and fish if it means sitting with hands in gloves and a half dead maggot dangling off a 16. A change of hook, bait, tactics and depth cam make all the difference IMHO, just as baiting several parts of the same swim if considerable differences in depth are to be found....
Invariably, working hard for you fish on cold days, which can mean changing your bait or combination every couple of casts is the way to go. Not easy to add or remove a number or 8 shot with cold fingers either, but it can make all the difference, regardless of maggot colour!!
Only my opinion, though!