1.clj

(defn xors
  "Returns bitwise XORs"
  [max-x max-y]
  (for [x (range max-x)
        y (range max-y)]
    [x y (bit-xor x y)]))

(def frame (java.awt.Frame.))
(.setVisible frame true)
(.setSize frame (java.awt.Dimension. 512 512))
(def gfx (.getGraphics frame))

(doseq [[x y xor] (xors 512 512)]
  (.setColor gfx (java.awt.Color. (mod xor 256) (mod xor 256) (mod xor 256)))
  (.fillRect gfx x y 1 1))

2.clj

(doseq [[x y xor] (xors 512 512)
        grey (mod xor 256)]
  (.setColor gfx (java.awt.Color. grey grey grey))
  (.fillRect gfx x y 1 1))

3.clj

(doseq [[x y xor] (xors 512 512)]
  (let [grey (mod xor 256)]
    (.setColor gfx (java.awt.Color. grey grey grey))
    (.fillRect gfx x y 1 1)))