The palette
Commit to the green. It is the dominant colour here and holding back on it would produce a print of nowhere in particular: let the commons, the Backs and the fens read as one pale continuous sheet, and let the old core sit on it as a compact grey, slightly warm, almost pink. Keep the Cam a thin line but an unbroken one, because the eye follows it round the whole loop. The station road in the south-east is the only frankly straight axis on the sheet; treat it as punctuation, not structure.