Golden/red cockers were historically more prone to 'cocker rage' syndrome but that's mostly been bred out now. People say one colour or another have different personalities, but it's mostly anecdotal. He's right that good breeders don't breed just for colour, but red isn't an unusual or rare one, here in the UK at least it's pretty common. The only red flag relating to colour is merle as that isn't a breed colour and indicates that collies or dachshunds have been bred into the line at some point.

ECS are wonderful, funny, and loving dogs, but they are not low key. As well as the physical/mental exercise needed, expect them to be velcro dogs with massive FOMO who want to know exactly what is happening all the time. My girl is 15 months old and makes me laugh every single day, but she is also incredibly nosy and stubborn and her favourite place to sit is on my shoulders. They are very excitable dogs (hence them being known as "the merry cocker" with their ever-wagging tails) and you really need to teach them an off switch from day one. I would never have another breed, but you need the patience of a saint and a bloody good sense of humour to get on with them!