Hi there! The general sprites seem quite readable to me, the only issue I can put my finger on is that you might be using too much colours, for example with sofia her pants and shirt(?) have a total of six blues that could be easily turned into five, (or even four). i.e. In my opinion there are some unnecesary colours.
I've edited one of the poses to show what I'm talking about (I turned the two midtones into one, as well with the dark shades, and edited the darkest and lightest a bit):
(I also edited the helmet a bit, just so you know)
With Sunita, it seems to me that her face, in the frontal pose, is a bit too long, maybe move the shoulder area up a pixel and make the face shorter by one pixel to compensate.
But overall these are pretty awesome sprites.
