The palette
The ground is a grey-beige weave with no accents, and against it the bayous should read as thin frank green: that is the master contrast of this map. Put your strongest colour in the motorway ring and the radial spokes, in clean lines rather than a wash. Water is three different things here: winding in the bayous, geometric in the ship channel, striped in the flood reservoirs to the west. A map has a single ink for all its water, and the drawing tells them apart. If you make it green for the bayous, the lakes and the channel will be green too: that is the choice our poster makes.