Custom potion colour

Ello My name is SmallEnderman and got a quick question

i've been doing alot of mythic mobs like items/skills/mobs ect... but i was trying to get an idea of custom potion colour and stuff like that... the effect are pretty ez to do... but idk how to customize the colour of a potion... does someone know how to do this? pls tell me

thanks for helping
~SmallEnderman