"My ketones are showing “green” in the mornings and “yellow” in the afternoon, using the Ketonix. When it shows “blue” it’s time to fast, exercise or have more fat!"

Right. So the guy is trying to maintain ketones.... actually only acetone, the most variable ketone. He pooh poohs beta-hydroxybutyrate and acetoacetate. When he wants more acetone, he fasts, exercises or eats more fat. He is not trying to lose weight. He is not trying to get the optimal RQ. None of that. He's just trying to get a lot of acetone.

I agree that the breath meter does a probably good job of measuring acetone as long as it's not fooled by ethanol. What I don't agree with is what that has to do with anything.