Aye. Now for the critique:
you've got a lot of jaggies and floating pixels. Those spots of lighter brown on the hair, the way the curves don't quite work, the banding on the hair, the low contrast on the browns...
Try to start with reducing your color count on the hair to two, maybe three shades of brown or brownish red. Light, middle, dark. Then use those to do the entirety of the hair. While doing this, try to keep pixels grouped as much as possible. Sort of like you're making the piece out of Tetris blocks!
As for jaggies, that's a bit more of an abstract concept, but basically, follow this guide here:
Another thing you're doing is using solid black as an inside color, it tends to draw the eye too much and distract from other details! Try replacing them with shades relevant to the part being drawn, like a darker tone on the skin for the nose ears and lip-line or the darker brown color from your new palette.
Contrast in your colors is also an issue throughout the piece here, now that I take a closer look. I didn't even notice the cheek circles until I spent a bit longer looking at it, same for the shading around the eyes!
Something that helps my colorblind butt keep it in line is a minimum of five to ten values on the hue saturation or value sliders for MINIMUM contrast. It takes a bit for it to click sometimes (it did for me) but once you start seeing how crisp higher contrasts can make the colors you use you'll start to really take it in!
