I expect most of these suggestions to be declined but will paste a few mods I found that add features that fit in with vanilla. (found all of these when going through all of the mods on 1.12.2 cuseforge.
https://www.curseforge.com/minecraft/mc-mods/colouredchat
https://www.curseforge.com/minecraft/mc-mods/placement-preview
https://www.curseforge.com/minecraft/mc-mods/colored-water
https://www.curseforge.com/minecraft/mc-mods/colorful-potions
https://www.curseforge.com/minecraft/mc-mods/coloured-sea-lanterns

That's all of these are small mods that I found that match vanilla to an extent

this is not the place for suggestions.

ok