Texture pack for 1.13 -> 1.19 are cross-compatible, difference is litteraly one number that just affect a warning before loading, so if you wanna use on any post 1.13 version of Minecraft just ignore this warning, all comment about version actually supported will be removed. 1.12 has to much changes in Optifine and this is not compatible with them.
gvzG
Similar to RandomColoredCreeper, ColoredVanillaSlimes and SpiderDiversity, this texture pack just randomly recolor a vanilla mob using Optifine feature. Simple way to add more diversity without break Minecraft texture style.
This texture pack need Optifine and random textures enabled (by default).
Nothing else to do, random color are assigned on spawn, 32 color variations + the original color.
Like Spider, eyes are another texture, this can't be changed now, that's Optifine issue
