Leaves got retexured in 2019 with 1.14, but Creeper which used the leaf texture did not. I used Bedrock's oak_leaves_carried.tga as the basis here. I think it make it too dark, but I'll have to see in-game. You obviously don't have to like it, I certainly don't. But, I think I'm on to something here. Maybe it could be lightened?

Played with it a couple minutes, and it looks good in game. Too light for some biomes, too dark for others. Maybe I need to make every leaf, and then decide. I might make the leaves from one or two mods, but no promises.

These ones are a little better in my opinion:

www.planetminecraft.com/texture-pack/creeper-new-leaf/
www.planetminecraft.com/mob-skin/faithful-jappa-creeper-v-2/