Flags need a standard meaning!

those suggestions you stated arnt what they mean. I think most people go by what the real flags did mean back in those days.

I think the only definitively shared meaning is Jolly Roger - pvp'er and White - we don't want any trouble. The other's a I chose based on ship skin.

Here's what I've gathered so far:

Blue - "Navy". Will hunt red/jolly rodgers, and aid those being attacked.
Red - PvP, will sink you at sight.
Yellow - Doing voyages. Looking to trade goods.
White - Surrender, parlay, passive.
Jolly Roger - Pirates. You will not be sunk if you give us what you got.
Shark Hunter - PvE, looking for help with forts/beasts.
Checkered - Looking for a race.
Black - Leave me alone.
Rainbow - Got newbies on board, perhaps?

@shuoink

I have also seen this in the reverse. A friend and I went full black sails and jolly roger and went looking for trouble. We found a galleon and were messing with them playfully (my friend smuggled himself on their ship and was fighting them off the crows nest while I chased after shouting they kidnapped my crew).

They shouted back that they were friendly and kept directing us to their white flag. "We just want to be friendly! Can't you see our white flag dude! We have the white flag dude!"

While I own up to our behavior by no means were we required to give them a pass just because of their flag stance. A rough guidelines for communication is nice but I will always be against a set in stone flag meaning system. You might as well implement server types at that point...

https://www.seaofthieves.com/forum/topic/63223/flag-meanings/2

@katttruewalker said

... if I'm sailing and we see a jolly roger, then we know the ship is likely out for loot and combat, a red flag likewise. If we see a blue or yellow flag then it tends to indicate neutral behaviour, possibly friendly crews and then the rainbow flag likewise.

A lot of crews flying the rainbow flag initiated combat on the day of it's release. In my findings, this has been on-going since then.

I think the meanings for the flags are likely to come about as a result of player behaviour that we experience when those flags are encountered. We always make a definite decision around what flag to fly when setting sail.

While it may be this way by your personal experiences, I assure you it's quite possibly been the exact opposite for us.

These flags are a great inclusion if SoT pirates could be trust worthy. lol Yeah right.
Many use the white flag and default ship livery to lure you in closer, thinking that they might be peaceful new comers, before they open fire at you.

Sloops also seem to be equally aggressive if not more so than galleons.
I suppose it's a lot easier for one aggressive player to convince his partner to attack (or simply continue to attack anyway without consent) rather than someone who may be out-voted by his other three crew members.
I have often been the only voice of reason in a crew of four and it usually turns out in a peaceful passing even though I'm just a deckhand and not controlling the helm.
It helps to mention how low we are on supplies or that I'll be leaving soon so let's finish the voyage and cash-in.
And I'll always say, don't fire first. See what they do.

I'm not apposed to some PvP, it's exciting. But at the same token I don't want to intentionally ruin the game experience for someone else.

Getting back on topic, many will just fly the coloured flag that best suits their ship's colours. :o)

You can make a meaning to the flag however you want...for me, and I'm sure for the most people they mean nothing but another cosmetic...

You put a white flag on...I don't care, I will sink you, when you're in the way
When I have the jolly roger on, I still will shoot only when you shoot first
These meanings ate completely useless