What happens when the carbon dioxide in exhaled air mixed with water and basic indicator?

Question

What happens when the carbon dioxide in exhaled air mixes with water + basic indicator?

Answer 1

limewater is a basic indicator of carbon dioxide, the limewater will go murky or milky when there is carbon dioxide present

Answer 2

Carbon Dioxide mixes with water to form the mildly acidic Carbonic acid (H2CO3).

I don't know what "basic Indicator" you are talking about but, provided it changes colour in the correct pH range, it will indicate that the solution is becoming acidic.