Anti-fouling paint (The paint on the bottom of boats and ships) is composed of either Cuprous Oxide (a form of copper) or Thiocyinate (sp?) a tin based compound. As of 6 or 7 years ago the Thiocyinate paints started to become illegal because they kill more than the barnacles that they were intended to kill. That leaves the Cuprous Oxide paints as the only anti-fouling paint left. The red paints have the highest amount of copper in them. Typical concentration is about 56% for Trinidad, a popular brand. The same paint but in blue, green or white ranges from 38% to 48% concentration of Cuprous Oxide. Since that is the active ingredient that kills the barnacles that slow down the ship and make it burn more fuel in the process, it just makes sense to paint it red and have it last a little longer as a haulout and repaint can cost thousands of dollars to the shipping company, not only to actually haul and paint the ship but the loss of a cargo carrying opportunity. I know this answers your questions. Sorry for the tremendously long run on sentence.
Marine Professional since 1977