I prefered this with some outlining, nothing too fab im kinda rusty but I definately think you could use this palette more efficiently. Most likely over done it with the dithering considering its still such a small character but still wanted to add some more interest here and there.
love the turtle
think you could have some improvements with the palette, but just thought I should show how you can make the most of what you have. If anything you could tweek values, hue and saturation to get it spot on.
Hope anything helps, looking forward to any updates.