Water for baby?

My son is going to be 6 months next week and I’m pretty confused about what I’ve looked up about giving them water. I think he was a little dehydrated yesterday and today because he had a little pink spot in his diaper both days in the morning when I changed him. It was only urine but I freaked out thinking something was wrong. I looked it up and found out it might be dehydration which might be possible because we were outside for an Easter egg hunt and then a walk in the park the next day and he is never in the sun much. My question is at what point do I need to give him a little water? Is it even necessary? I’m breastfeeding and I thought that milk would give him the water he needs but since he’s been sleeping longer at night I’ve been pumping and he didn’t drink a couple of those bottles which I think has more water in them since they were more clear than yellow... could he be dehydrated?