At 600 pages, this is a long story, and a substantial part of it is taken up by events that happened before the long voyage and during it. Particularly significant here are the roles of Just and 'Colin', two people who were chosen for their youth and therefore their supposed facility with languages, indicating that they will be able to communicate with the native Indians and quickly serve as interpreters for the French. However, they turn out to be a little older than expected, and they (unknown even to themselves) are not the siblings they were initially thought to be – and (to the surprise of the crew) 'Colin' in fact being the female Colombe.
Colombe does in fact mix with the Indians very well, learning the language quickly, joining them in their nakedness, and forming friendships with them. She sees herself on equal terms with them (and certainly they don't eat French people!), unlike her arrogant European counterparts, who at first see the Indians as potential slaves, savages who should wear clothes to conform to Western standards, etc.
Indians are also useful, of course, for trading purposes. And trading is vital here. The rouge doesn't only allude to the Indians' skin and cosmetic colourings, or to the great amount of blood that will be spilled here, but also to the highly esteemed red wood from which Brazil takes its name, and a great deal of which loads the ships' cargoes for return journeys.
This is a Foulcauldian universe in which diverse powers strive for dominance, where people act as double and triple agents, the duplicity can be cut with a knife, the 'reinforcements' brought from the continent bring about even more of a war of religions, more bloodshed, more tension. Here there is traffic in convict slaves, the existing French interpreter Le Freux can sell the local Indian-made alcohol (partly made from the women chewing manioc) and the local girls to sexually service the crew, boiling the religious wrath of Villegagnon: And this is really just the start of the problems: the Portuguese haven't even come to have their say in the invaders' activities, for instance. An interesting book about interesting events, and the author's Afterword attests to his assiduous researches behind this novelization.
My other Jean-Christophe Rufin posts:
Jean-Christophe Rufin: Sept histoires qui reviennent de loin
Jean-Christophe Rufin: Le Collier rouge