We realize that the glass might seem dark with certain lighting conditions. Unfortunately, any lighter version would not have proper reflective capability during the day and thus would render the device useless during the day.
If you find it distracting, please try to reposition it on your dashboard and correct the angle of the glass. Also, please try using the device in all lighting / weather conditions. Perhaps you will find it less distracting at night? Another suggestion would be to play with brightness of the screen.
If none of this helps, it would be best not to use the device any further to avoid being distracted while driving.