I'm a musician who doesn't have absolute pitch, but does have very strong relative pitch. My understanding is that perfect pitch is neat party trick, but actually a hindrance instead of a help in most musical circumstances. Relative pitch, on the other hand, is incredibly useful (and fortunately you can train and develop it later in life).

Because most people don't have perfect pitch, (Western) music is built on the relationships between pitches rather than the absolute pitches. So with absolute pitch, you can play something by ear; with relative pitch, you can play something by ear in any key.

Learning to think of the notes you're playing relatively instead of absolutely is already a difficult leap for most musicians, and my understanding (though I don't have absolute pitch so I can't compare from experience) is that absolute pitch makes this skill significantly harder to acquire, since you have to retrain your ear in addition to your hands.

If I were offered a choice to trade my sense of relative pitch for absolute pitch, I most certainly would not take it. I know well the feeling of incongruity when my muscle memory is stuck in the wrong key, and absolute pitch would mean I'm stuck there all the time instead of being just able to shake my head, focus on the new key, and clear my mind of the old.

The only age-sensitive part is the ability to map the chords to the colors.

Eventually, you would want to teach them to map the color to the chord name and recognize the root of the chord. But that can be learned any time.

Also keep in mind that if a kid learns all the colors, you'll want to continue practicing to "bridge" over the age where they would lose the ability to recognize perfect pitch. If they mastered this at age 4, they could still potentially lose the ability if they don't practice during that period.