"The dark blue is full fat but 'light blue' is light," she said.
"Pink milk is skim – not to be confused with trim [low fat] red milk. Aren't they the same?"
"And then there's a purple for lactose-free which can also be green … and don't forget yellow which is reduced fat but it's different from light, skim and trim.
"Then you have grey, which is cold-pressed … how do you press a cow?
"I don't even know what the black ones are for. And then gold is homogenised."
Grace's post has attracted 1.3 million views, with many foreigners admitting they're confused by the country's milk range.
"Forget it, I will not have milk as it is confusing and I will spend a million hours in the store," one TikTok user wrote.
"I'd just give up drinking milk to be fair," a second person said.
Meanwhile, some Aussies confessed they never noticed the different coloured milk lids.
"So people use lid colours to differentiate types of milk?! I've always just read the labels," one person wrote.
"In Australia, we don't need to pay attention to milk because we pick one type and brand and buy the same one for the rest of our lives," another person said.
"I think you've blown every Australians [sic] mind … we never knew there was a colour system," a third said.