It's a great start for your first pixel, but the most obvious thing I notice is that you need to add more shading, it looks very flat. I'm assuming he's made of metal, yes? Well, metal reflects light a lot and, depending on the shape, in many places! For example, the red light on his antenna would reflect onto his head, and a few other places, like the hand holding the bee, and his feet. I'm guessing that there would probably also be another light source (unless he's in a darkened room), which would also reflect off him in other places. And, more often than not, the surface he's sitting on will also reflect back onto the lower part of his legs / feet / body, etc.

And I just think the lineart will need cleaning up a little, but other than that, I think the design is great! :)

This has the potential to become a really good piece, but it needs a lot of work.

edit:


Sorry about the really dodgy digital painting type edit, it's far from perfect, but I thought it would be a good, quick way to show you some of the things that need to be done:

consider:

*increasing the contrast A LOT! -  Don't use colours that are too similar, it's extrmely hard to notice the difference. Also, it's a good practice to try and reduce colour count
*This guy is made from metal, try and think about how metal reflects light. Get a metal object and look at highlights, shadows, colours.
*Look around the gallery for other robot/metal related pixel art, see how others have done it.
*Your red light still needs a significant amount of work...ignore my edit in relation to it. But that red light would have more impact than just making a small highlight along the robot's outline.