Why are "floodlight purple balls" used during the winter of the EPL?

Question

Just watched the build up to Arsenal vs Man Utd on Sky Sports and it said that during the winter, floodlight purple and yellow footballs are being used for the next four months. Why is this?

Answer 1

I've never heard of or seen purple balls before, but yellow/orange balls are used during the winter to increase the ball visibility in case the field is snowy. (White ball on white field, almost like playing in the dark)

*edit*: just realized the 2nd color on the ball is purple, it used to be blue

Answer 2

Incase it snows which is highly unlikely in this country anyway.