It's hard to give feedback with something this basic, since I can't even tell what you're aiming to depict, if anything.
The yellow vibrates against the blues, I feel like you should probably use less saturated blues.
In the bottom version with the dark background, the entire structure feels more "solid", like it might be something the player can collide with, while in the top version, it feels like it should be entirely cosmetic. Perhaps that's something to take into account. Of course, value is far from the only factor that makes things look solid or not, so once you're playing with the saturation, hues, and details, the values may become a lot less relevant for this.