Don't read this if you want to keep that innocence...
Ok, you were warned. It's very simple: if there is a child in a pool then there is pee in that pool. If there is an adult in a pool then there is probably still a little bit of pee in the pool. The thing is, urine is sterile when it first exits the body. And in a properly sanitized pool it reacts almost instantly with the chlorine or bromine to break down in to benign salts. So people who run the pools just track the chemical levels as required, and they recognize situations where they sometimes should check a bit more often
Oh, and the concept of a chemical that turns color when someone pees in the pool is a myth. I guess years of being told that by lifeguards and camp counselors has worked wonders, a lot of adults still think such a thing exists. I bet someone reading this is even convinced they saw it demonstrated (spoiler: it was leak detection dye in his swim trunks). But as I pointed out, a bit of urine in a properly managed pool is not a problem so ignorance is bliss.
As far as #2: just know there is a very tiny amount of fecal matter in every pool that has a person in it up to their waist, but again the chlorine makes short work of the nasties in it. Really a "code brown" is more for the mental health of people, showing that something is being done about it, than for physical health.