The warning levels are fixed, based on current regulations, and cannot be changed by the user.Green: Tyre pressure +/- 15% of target pressure - no action required. Yellow: Tyre pressure +/- 15% - 25% of target pressure - correct tyre pressure at next opportunity. Red: Tyre pressure +/- 25% of target pressure - stop immediately and correct tyre pressure. Garmin devices can customise the alert threshold in the Connect IQ app.