How do we distinguish a single instrument's sound when listening to a orchestra??.?

People do not generally have any trouble telling red from green or blue when all are presented at the same time. People also can smell the difference between lavender and cedar and taste the difference between bananas and peas. Each item gives off a distinctive essence that is unmistakable. And so that is true of sound. People with perfect pitch have often commented that the note Bb is as different from G# as radishes are from oranges. Which means we all have the ability to hear these distinctions on some level, some of us are just more aware of it or familiar than others. The more you listen and pay attention the easier it becomes. All can hear some obvious instruments like drums from flutes some can hear more subtle differences say clarinets from saxophones.