Tray states

The tray icon is the app’s whole interface while you work, and it follows one rule: blue means the microphone is live, and how full the swirl is shows what is being heard.

• Idle. Dim arms, no blue anywhere. The microphone is off.
• Armed. A blue outline with empty arms. The microphone is hot, nothing is being picked up.
• Speaking. The same blue outline, and the arms fill with light blue from the centre as the level rises.
• Paused. Violet with two white bars. Transcription is held until you resume.

No other state introduces blue, so a glance is always enough to know whether you are being heard.