Actually this pattern should not that hard to implement. If you look at the streets, they are mainly 4 blocks wide, with the outer blocks being lighter than the two inner ones (with some random exceptions). So for every block you could check it’s neighbors (which would be 4 if you only consider the 90° direct neighbors). Now if any of these neighbors is grass/not-a-street, you choose the “rim color” (in this case light) and mark the block internally as “rim”, otherwise you mark them as “inside”. Now if an “inside” block has at least 1 neighbor marked as “rim”, you randomly assign either the light or the dark color to it (with a sufficient low probability for only 1 rim neighbor, and a higher chance for 2 or more neighbors, to keep inside edges this way). Otherwise, an “inside” block with no “rim” neighbors always gets the inside/dark color.
Well… my gardening level is not that high, but I hear, real pumpkins actually just need lots of water to grow to massive size… But yes, for Stonehearth at least I’m hoping for something more dramatic!