I thought it was so they saved money on making the caps, not having to use different colours. If thats also true i hope it passes the saving onto the consumer (ik it wont but one can dread)
Personally I'm an oat milk man. Primarily because I kept getting confused since Aldi's soya milk (yum) and almond milk (boak) have nearly identical red colour packaging, while the oat is totally different.
But... If I had to do cow juice, it's true blue baby. All the rest is water.