You have to take into consideration the NES palette limitations.
You can't have more than 3 colours per tile and I can see Yellow, blue, purple and red in there.
I say simply change the sky blue colour to the purple one and it might be doable.
Of course, this image has no useful value, predates the first published image, the uploaded because only after trying it I noticed the challenge confronted by Vanya, is really admirable the way they run her work.
For this reason it seems to me very difficult to apply my image to the format that seeks. I tried several styles of I color and when I apply the restrictions that are perceived in the original image can not achieving anything sufficiently balanced.