Alright lemme step in.
While it's not bad for a first, you should never really jump into pixel art before trying out real art. You'll reek of inexperience, as does this.
Show me ANY object in real life which hair as bright as that and I'd be shocked. Also, you've shaded the hair strangely -- just noise, rather than shadow. the back of the head should be mostly darker than the top of the head, providing your lightsource is roughly above.
Your tones are too close together, and also the hair casts no shadow on the face -- which it should.