Wow, that is a nice shot! Very nice and sharp! The backlighting really brings out the colors. I also like the composition, the leaf is not just smack-dab in the center of the frame. The background is nicely blurred, the 50mm 1.8 as good at that I hear! I think the picture could have been stronger if the background could have been all blue i.e. just the sky, instead of the other leaf which sort of blends in.
Overall, I think it’s a very nice picture, I would have been happy to get a picture like that!
Looking through a leaf toward direct sunlight is the best way to get the vivid colors, for sure! However, I just don’t get the feeling that the leaf is “vivid”. It’s got incredible texture, but it seems to be a little overexposed in the leaf area, perhaps. Perhaps adding vignette in LR would do the trick too.
There seems to be a lot of blotches on the leaf. Either edit those out or look for a more “perfect” specimen. Every element in a close up shot is important. This shot from Florida is spotless, and it has to be to keep the eye from being distracted in the subtle spiral.
Also, while seeing the edge of the leaf provides interest, I think the eye should be more directed to the veins. I would either zoom in more to get just the texture of the leaf or zoom out a little so that the edges of the leaf become a shape that works with the veins.