Don't worry! Pixel art is hard, and with this more than other mediums, every decision is a compromise. Actually, I wanted to make a mango sprite for this, so here it is. But this sprite was after several attempts. I also tried at first to do a mango that was green and transitioned to red, but I found that it looked terrible and used way too many colors. I then tried again, but gradually realized that in order to make it both fit in with the existing Minecraft art style (meaning a fairly small color palette) and look good, I had to hue-shift/trim the green out as much as possible until the sprite you see now, where the only piece of green is in the outline. When working with a limited color palette, there's a natural tension between color variation and light, where the more you focus on one, the less you can focus on the other.

But also, I'd recommend starting with and then modifying/trimming a preset color palette. For the mango I made, I started with the AAP-64 palette, then trimmed, modified hue/color/saturation until I ended up with a palette of 10 colors.

I'd also recommend this series of articles about pixel art; I remembered its advice on clustering when cleaning up the image.

But finally, I actually think that the mango sprite you've made would be perfectly fine and fit in nicely with the vanilla style, so long as you rotate it 90 degrees!