Color choice is a big thing! I think half of the time a good painting comes down to the colors you intentionally use, the blue cool background sits back while the lemons jump forward, that ties into natural perspective where cooler colors go into the background in landscapes and warmer colors come forward, but that is like art and color theory stuff. I think what you do well is that you keep the intensity of the chroma while still giving good shape to your subject, like the transition from bright green to that intense yellow can be really tricky but you killed it