With tongue firmly in cheek, and as an alternative to the various "lighting" proposals, I did consider posting whether it would be possible to install a noise generator, or a rotating indicator on the front of a turbofan, so that you could get visual or aural warning of its operation.
In all seriousness, we often see the rotating nose cone (often with an spiral motif) on some installed turbofans. However, whilst I am not familiar with the Embraer in question, photos on the web seem to show that the engine nose cone is positioned well down the nacelle intake, and by the time you saw it you would probably already be accelerating towards it.