Its easier to understand from the pics in the Ravelry link in the description but its columns of squares, except in the case of blocks of colors then its larger squares to reduce the need for more stitching after. Thank you!
In the Ravelry link you can see it was split into 5 columns of 5 pixels per column. It was a combo of individual blocks but color switching along the single pixel verticals. Unless there were larger sections of similar colors, then I tried to keep them together to reduce the amount of post-stitching required.