While the official Minecraft texture did a pretty good job, I could still make it more true to it's real life counter part.

While it's rather similar to the original texture, I lightened up all of the colours so it wasn't such a vibrant pink.
Remember that similar to albinism, leucism is a lack of pigment (it only affects skin, scales and feathers).

So the actual animal's skin doesn't have pigment, the colour is coming from the blood underneath the thin skin.
So it can't be too vibrant, just a soft pink colour.

Also changed the feet so they're more white at the toes and tweaked the eye colour.
Tail is also tweaked to gives the edges a more transparent feel.

The gills actually stayed the same as they were already the correct shades, they now look better in contrast with the lightened body.