The palette
The subject of this sheet is a boundary, the one between water and land, and it is absurdly long: every cove and every islet adds to it. So take a clean contrast between the two, with nothing in between, or the shoreline blurs and the point stops being visible. Green here genuinely exists, in frank enclaves rather than as a continuous ground: let it live in the south and the east, it holds the sheet down. And keep the streets pale: they are not the subject, they are what fills the point.