As for a color opinion, I too like the look of light blue for depth but am going with black for now because of the black overflow.
Maybe down the road when the box is covered in algae I'll try blue. Cheap enough to try
Word of warning with this idea though;
Don't splash water on the back glass unless you can reach back there to clean it! I ended up with streaks on the 125g and couldn't clean it. It stood out badly against the black.