diff --git a/inky/inky_e673.py b/inky/inky_e673.py
index 86e91b3..4d9c580 100644
--- a/inky/inky_e673.py
+++ b/inky/inky_e673.py
@@ -79,8 +79,8 @@ class Inky:
     WHITE = 1
     YELLOW = 2
     RED = 3
-    BLUE = 5
-    GREEN = 6
+    BLUE = 4
+    GREEN = 5
 
     WIDTH = 0
     HEIGHT = 0
@@ -308,16 +308,34 @@ def set_image(self, image, saturation=0.5):
         """
         if not image.size == (self.width, self.height):
             raise ValueError(f"Image must be ({self.width}x{self.height}) pixels!")
-        if not image.mode == "P":
+
+        dither = Image.Dither.FLOYDSTEINBERG
+
+        # Image size doesn't matter since it's just the palette we're using
+        palette_image = Image.new("P", (1, 1))
+
+        if image.mode == "P":
+            # Create a pure colour palette from DESATURATED_PALETTE
+            palette = numpy.array(DESATURATED_PALETTE, dtype=numpy.uint8).flatten().tobytes()
+            palette_image.putpalette(palette)
+
+            # Assume that palette mode images with an unset palette use the
+            # default colour order and "DESATURATED_PALETTE" pure colours
+            if not image.palette.colors:
+                image.putpalette(palette)
+
+            # Assume that palette mode images with exactly six colours use
+            # all the correct colours, but not exactly in the right order.
+            if len(image.palette.colors) == 6:
+                dither = Image.Dither.NONE
+        else:
+            # All other image should be quantized and dithered
             palette = self._palette_blend(saturation)
-            # Image size doesn't matter since it's just the palette we're using
-            palette_image = Image.new("P", (1, 1))
-            # Set our 6 colour palette and zero out the remaining colours
-            palette_image.putpalette(palette + [0, 0, 0] * 248)
-            # Force source image data to be loaded for `.im` to work
-            image.load()
-            image = image.im.convert("P", True, palette_image.im)
+            palette_image.putpalette(palette)
+
+        image = image.convert("RGB").quantize(6, palette=palette_image, dither=dither)
 
+        # Remap our sequential palette colours to display native (missing colour 4)
         remap = numpy.array([0, 1, 2, 3, 5, 6])
         self.buf = remap[numpy.array(image, dtype=numpy.uint8).reshape((self.rows, self.cols))]
 
diff --git a/inky/inky_el133uf1.py b/inky/inky_el133uf1.py
index b35506f..fbe2353 100644
--- a/inky/inky_el133uf1.py
+++ b/inky/inky_el133uf1.py
@@ -97,8 +97,8 @@ class Inky:
     WHITE = 1
     YELLOW = 2
     RED = 3
-    BLUE = 5
-    GREEN = 6
+    BLUE = 4
+    GREEN = 5
 
     WIDTH = 0
     HEIGHT = 0
@@ -326,22 +326,41 @@ def set_border(self, colour):
 
     def set_image(self, image, saturation=0.5):
         """Copy an image to the display.
-        :param image: PIL image to copy, must be 1600x1200
+
+        :param image: PIL image to copy, must be 800x480
         :param saturation: Saturation for quantization palette - higher value results in a more saturated image
+
         """
         if not image.size == (self.width, self.height):
             raise ValueError(f"Image must be ({self.width}x{self.height}) pixels!")
 
-        if not image.mode == "P":
+        dither = Image.Dither.FLOYDSTEINBERG
+
+        # Image size doesn't matter since it's just the palette we're using
+        palette_image = Image.new("P", (1, 1))
+
+        if image.mode == "P":
+            # Create a pure colour palette from DESATURATED_PALETTE
+            palette = numpy.array(DESATURATED_PALETTE, dtype=numpy.uint8).flatten().tobytes()
+            palette_image.putpalette(palette)
+
+            # Assume that palette mode images with an unset palette use the
+            # default colour order and "DESATURATED_PALETTE" pure colours
+            if not image.palette.colors:
+                image.putpalette(palette)
+
+            # Assume that palette mode images with exactly six colours use
+            # all the correct colours, but not exactly in the right order.
+            if len(image.palette.colors) == 6:
+                dither = Image.Dither.NONE
+        else:
+            # All other image should be quantized and dithered
             palette = self._palette_blend(saturation)
-            # Image size doesn't matter since it's just the palette we're using
-            palette_image = Image.new("P", (1, 1))
-            # Set our 7 colour palette (+ clear) and zero out the remaining colours
-            palette_image.putpalette(palette + [0, 0, 0] * 250)
-            # Force source image data to be loaded for `.im` to work
-            image.load()
-            image = image.im.convert("P", True, palette_image.im)
+            palette_image.putpalette(palette)
+
+        image = image.convert("RGB").quantize(6, palette=palette_image, dither=dither)
 
+        # Remap our sequential palette colours to display native (missing colour 4)
         remap = numpy.array([0, 1, 2, 3, 5, 6])
         self.buf = remap[numpy.array(image, dtype=numpy.uint8).reshape((self.rows, self.cols))]
 
diff --git a/tests/test_e673.py b/tests/test_e673.py
new file mode 100644
index 0000000..0092fb6
--- /dev/null
+++ b/tests/test_e673.py
@@ -0,0 +1,13 @@
+def test_set_image_p256(GPIO, spidev):
+    from PIL import Image
+
+    from inky import inky_e673
+
+    img = Image.new("P", (800, 480))
+
+    for x in range(256):
+        img.putpixel((x, x), (x, 0, 0))
+
+    inky = inky_e673.Inky()
+
+    inky.set_image(img)