Is there any simple and easy way to convert a player's ID into a vector3?

While that isn't possible without hacky methods like tostring, tonumber, and string.sub being combined with Vector3's-

Wrote the coded & commented it; untested, and it may or may not work. But something like this definitely will!

_G.Colors = {} --\\Make a table of colors already used. In _G, too, so any script can get a players color.

local Start = 1 --\\Minimum color

local End = 64 --\\Maximum color

math.randomseed(tick()) --\\Set the random generation seed, makes the result seem more random.

local function TableHasValue(Ki) --\\Define the function for checking if a Ki is used.

	for Index, Info in next, _G.Colors do --\\Loop through used Ki's

		if (Info[2] == Ki) then --\\If it is taken then..

			return true --\\It's taken; return true. Find a new Ki.

		end --\\End the if statement.

	end --\\End the loop

	return false --\\Nothing found, it's untaken; return false. Not necessary but I like to always have an explicit return value, not implicit (nil or otherwise).

end --\\End the function definition.

local function GenerateKi() --\\Define a getKi function.

	local CurrentKi --\\Define an empty variable to the ki

	repeat --\\Start a loop

		CurrentKi = BrickColor.palette(math.random(Start, End)) --\\Select another random Ki

	until (not TableHasValue(_G.Colors, CurrentKi)) --\\Stop if it's an untaken color

	return CurrentKi --\\Return the Ki

end --\\End the function.

--[[
	Example use:
	_G.Colors[#_G.Colors + 1] = {Player.Name, GenerateKi()}

	INFO:

	To get it as a GUI Color (Color3) simply do GenerateKi().Color

	Ki's are formatted as {PlayerName, KiColor}

	If there are more players than the possible amount of colors, it WILL crash!
]]--