I gave this a rating of VERY difficult because it was SO fidgety--too many single cells of color with too many very close colors...almost quit. I usually try to be very positive on this site, but Geez! it had to do it over 3 sessions! Who is this guy again?
Yeah, it took me 40 minutes, and most of that was just fiddling with four shades of grey and three shades of blue. Still, I think the end result comes out pretty well. I was close to using the custom palette, but I ended up barely deciding not to use it.