What color do you enjoy?
There is no limit to your enjoyment.
I suggest you get a color you can see even if you are color blind. Bright colors help to see the line if it falls in the water.
Getting a floating line will help keep the line from riding down and under the boat where lines can get in all sorts of trouble.
Seeing that this is posted in the racing forum, you could really mess with opponents if your chose Chartreuse and Pink...