Change potion color withou mods

[obtuse frigate]

Is there a way to change vanilla potion collors without polytone or something similare
if not is there something that works for 1.21.6/7

[silent elbow]

you can modify the itemdefinition of the potion

https://minecraft.wiki/w/Items_model_definition

please note that there is a difference:
Item model: defines the shape of the item
Items model: defines which model is being rendered (and handles tints)

[silent elbow]

then you can have it allow for a tint using custom_model_data

[spice blade]

you can't change the default colors of potions with just a vanilla resource pack, no.

[obtuse frigate]

can I make it use a diffrent texture based on some property of the potion?

[spice blade]

that you can do, yes. you can use the items model definition as theblackswitch already pointed out. for that the most likely choice would be a select model type with the component property testing potion contents

[obtuse frigate]

Then I could just brute force old potion colors by having texture for every potion type
If I understand correctly

[heavy folio]

yea

the texture would be the same bottle with just a different color