The palette
Water does two jobs here: the lake across the sheet, broad enough to carry a deep ink, and the two creeks, thin enough to disappear if the ink is too pale. Choose it for the creeks, since they are what frame the old plan. Green follows the creeks too, and gathers in the Capitol grounds and the park along the southern bank; a green clearly set off from the water keeps the two lines distinct where they run side by side.