Historical research is often the first step in building a custom ship model. Sometimes drawings of the vessel have survived; this may be particularly true for Navy ships, not so much for merchant vessels. Depending how far back in time we go, the information becomes sparse and much harder to find. A variety of artwork such as carvings, etchings, paintings and even surviving models, may sometimes be our best source of information for vessels of the 16th century and earlier.
Photography doesn't help us at all unless we get to the latter half of the nineteenth century. For all intents and purposes no photographs of vessels exist from before the late 1850's. Of course the color scheme is also hard to discern from the shades of grey on black and white photography.
Contemporary paintings can give us very valuable information if we keep in mind that the artist may have used a bit of artistic license. Quite often paintings of the same vessel show her quite differently. Sometimes this can be contributed to the ship's configuration and paint scheme changing over time, sometimes it can not. Even after Naval paint schemes became somewhat standardised, a captain's preference often played a role in the selection of paints and colors.
It is this gathering of bits and pieces of evidence that will create a defined outline of what the ship should or could have looked like. An image of the model is starting to develop.