On the right track, but I think you need to slow down.
Another edit:
List of Changes:-Reduced the size to 75% of what you had. Your canvas right now is pretty big, pixel art works better in smaller sizes, otherwise you get bogged down filling in the details of the res and make yourself work more too.
-Added another value to bridge the purple and black.
-Took the brown from the BG and worked it into her cheeks to help balance the blue and breathe some life into her.
-Shoulders are way too broad.
-Wasn't sure what was going on with the orange so got rid of it. I guess it was to balance out the blue? It overpowers it right now and confuses the eye.
The main point:Use more concise, confident strokes. (Smaller canvas makes this easier.) Your lines right now are all over the place. Look at Night's face edit and notice how clean the values are. You don't have to work so sketchy, think about the placement of your clusters/brushstrokes/pixels. One plane of color next to another will define the form, then blend where necessary.
Also I would say to be cautious about using other paintings as reference. A photo or real life is always ideal. A painting already has an abstracted degree of separation from the subject so you're starting away from the real thing already. Still, it would be interesting to study the brushstrokes and make your clusters based on them.
Keep at it. You're getting better. The blue highlights are a cool idea and works well.