Paint Colour on a Ship's Hull Draft Region?

The following 2 questions has always interested & confused me at the same time. I've never actually read anything that explains it to me. This will take me sometime to explain, so please excuse me for the length of my question.

1) Why do they paint the draft line black followed by the area of the hull below the waterline in red?

I understand how to read draft lines, therefore I can only assume it's to do with making it easier to see whether the ship's design draft capacity is over- or under-limit if the red is seen above the waterline. Is this true??

Ok, now that presents me with my second dilemma.

2) Why do ship modelers persist on painting the hull below the waterline shiny/glossy or even unweathered red/dull-red or hull-red?

I ask this question cos every picture I see of ship in drydock, even if it's before launching or when it's in for repairs, it has a faded orange-red colour - which is no where near the colour us ship builders paint. Some of us get so caught up in finding out the exact hull & deck colours, and the colours of every damn object on a ship, and then we weather the ship to some degree, all the time forgetting to think about below the waterline. You see it all the time with ship modellers painting rust markings on the hull which seem to disappear as soon as that shiny red hull is reached.

The only time I see a dirty weathered hull is on sub models, so why should ships be treated any differently - I've heard of the expression to keep everything in tip-top condition on a ship, but doesn't it seem a bit strange?

Any explaination would be helpful!