Well, to be honest, I think the colour is a LOT off, but you can correct that easily if you shot in raw. That said, congratulations for actually shooting a portrait; something many people seem genuinely afraid of. There is definitely some room for improvement here, so bear with me:
Laughing: This is both an awkward crop and an awkward pose. You've cropped her near shoulder partly off which is generally regarded as a portraiture 'no-no'. It's fine to crop limbs, but always do it boldly and never at a joint or along the longitudinal axis, and never crop "bits" of the body off. Her arms pushed out and held taught make them look skinny; not slender, but skinny. Young girls can be very tricky to pose when they're especially slender and you want to take care to avoid making them look skinny. Have her relax a bit and let them assume their natural shape. The same with her head/face; chin down, relax the jaw, and look toward (not necessarily at) the camera.
Box: Cute! I would correct the colour in this (it's off, but not badly, and crop the bottom just a bit higher so as to eliminate the "bit" of boot showing. This is the winner of the set IMO.
Upclose: The colours are almost spot on here; a slight green tinge in areas which I'm guessing is reflection, but that's minor. I wish You'd not cropped the top of her head off; shooting in vertical or portrait aspect would have been much more appropriate here I think. I would also pull down the highlights just a bit as some are verging on the blown.
Polkadot: The weakest of the set I think. The colour of her skin is badly off, the highlights toward the bottom of the image are extremely strong, and her face is in deep shadow. The human eye is always attracted to light over dark, so this really causes the viewer to look away from her face. You could easily have mitigated this with a simple reflector; a piece of white card, a white shirt, anything to get the light up to her face. You've also posed her square to the camera, often referred to as "football shoulders". This pose is rarely appropriate in portraiture and almost never for a young girl (Unless she is a football player). Always turn the body a bit in relation to the camera.
Overall I think these are a good start, and most of the issues can be corrected or improved with a little further work in post!
