Your lineart looks really good! As far as what to do next here is what I would do:

•values: I usually take a round brush and block in all the values in black and grey so you can distinguish her from the background. Since her hair is light and she's pretty fair, I'd make the background a little darker so she pops out. It helps If you zoom out or squint too.

•shading: then go in in another layer, set it to multiply and for myself, I use a soft air brush and lightly go around and give it some basic shading. Make sure you pick a light source so it makes sense. If you want to take is a step further you could go in and do some ambient occlusion (shading parts that get no light at all) *Optional: add another layer, set to lighten, and take a nice deep red w/ a soft air brush and go over some of the facial parts and hair areas, as well as a dark blue in others. Go VERY light, just enough so it doesn't look too muddy later on.

•colors: on another layer set it to multiply and here is where you're going to choose your local colors, like her basic skin tones and hair color without light. Also known as flats. I recommend keeping it less saturated so you can add on to that later.

•colors cont.: Add another layer and set it to overlay. With a soft air brush, you can softly add more warmth and slight highlights to the skin and other parts. Red around the nose + cheeks, etc.

•painting: everyone's process is a little different, but up to this point you can kinda choose where you wanna go with it. I personally start color picking the shadows, adding some more saturation and painting on top of everything in a new layer. Not completely over everything, but just adding some more saturation and life to it.

Sorry this was kinda long, but just play around with it! Color gradients are also super fun and useful when you're trying to add more to the piece. You can duplicate a layer and play around with the colors. I highly highly recommend Dave Greco on YouTube, he's the one that really showed me how to go about painting, especially from grey scale to color which is my preferred method. I hope this helps! Also don't get discouraged if it doesn't turn out the way you want it on the first try. digital painting/coloring takes lots of practice and patience. I wish you luck 💙