A yellow light indicates the side change or the second training round on the device. The duration of the yellow phase is 30 seconds. During this time, the trainee should change sides or can prepare for the second training round.
If the LEDs light up in a dimmed light, no member is currently logged in. If the LEDs are intensively shining, a member is currently logged in.
More about smart flex you find here.
The operating instructions for the devices are stored here.