The palette
Water is the whole figure here: a single ink for a river that crosses the sheet twice over. Take it deep enough to hold its own against the dense streets on either bank, because the double turn is what makes the city recognisable at a glance. Green comes in small doses, City Park in the upper corner and scattered squares; a soft tint is enough. The splayed streets need nothing but the streets themselves: a darker line for the major roads, a lighter one for the rest, and the pattern reads on its own.