The lighter the tub, the better the SHELL illuminates. Once the pumps are on, especially when the water gets olds this becomes less of a enefit as you dont really see the shell as much. The light will still alter the colour of water either way.
I still prefer lighter acrylic for one more reason, water marks. Especially if you are considering a marble/pearlescent acrylic.
If you are ina climate where there is snow, think about the salt marks on black/blu cars....
HTMan