Well something you captured perfectly is the adorable Rakshi head-shape. (yes, cute. It's always reminded me of reptiles, and reptiles are cute.) Perspective and proportions look good, too. So do the hands.
I generally like the design which is somewhat set-like yet also shows some stylization.
As for colouring; I don't really know what the colours of a Vacuum Rakshi are supposed to be like, so I can't comment on that. I was just wondering what kind of texture you were going for; for a metallic surface, some highlights and/or reflections would have been great, particularly around the eyes and near the glowing thingie on its back.
It's just a pity that you used lined paper, because the lines are a bit distracting; yet I know that this started out as random scribbling, so it's okay. ^^
Overall it's a cool piece of artwork! =)