They do look better, yes. IMHO, anyway.
Still, I tried cleaning them up a bit more:
I think it helps judging the colors a bit better if I use a medium-dark grey background, so I put them in one.
I tried making the tank a bit less organic looking (dunno if I was successful or not) by using more regular forms and 45 degree angles.
I can't understand the forms of the bike very well yet, so I invented a little.
Reshaded a bit of both to try and get a more consistent lighting.
Tried to hue-shift the colors on the bike so it doesn't look too monochromatic.
Didn't mess up with the enemy, but it does have lighting/shading problems as well. There's some pillow shading/banding going on and it's a bit too dark.
One problem that I can see right away (yet unrelated to color or readability) is that the background kind of tries to follow some perspective by having the floor at an angle and the platforms perfectly horizontal, but if your tank for some reason has to go down to the floor level, then it will (may?) look inconsistent. I mean, it does look a little already because the treads are not aligned horizontally.
