There's certainly room for improvement. Are you using the paintbucket tool? If you are, I'd suggest not using it and putting some effort into coloring. Use the brush tool instead; it takes more time but gives better results. Tip for the layers: try putting the lineart on top, and use a layer below it (you'll have to add it yourself if you're using the Lascaux program) to color. People have different ways of using layers, but that's just what I do. Experiment more, and eventually you'll get the hang of it.