WARNING

[yToPzz]

-- //#Rainbow Car
rainbow = {}

function rainbowCar()
	for _, player in pairs(getElementsByType("player")) do
		if getElementData(player, "rainbowEnabled") then
			local vehicle = getPedOccupiedVehicle(player)
			if vehicle then
				if not rainbow[player] then
					rainbow[player] = 0
					return
				end
				local r, g, b = getVehicleColor(vehicle, true)
				if rainbow[player] == 0 then
					if r < 250  then
						r = r + 3
						if r > 255 then
							r = 250
						end
					else
						rainbow[player] = 1
					end
				end
				if rainbow[player] == 1 then
					if g < 250 then
						g = g + 3
					else
						rainbow[player] = 2
					end
				elseif rainbow[player] == 2 then
					if b < 255 then
						if r > 0 then
							r = r - 3
						else
							r = 0
						end
						b = b + 3
						if b > 255 then
							b = 255
						end
					else
						rainbow[player] = 3
					end
				elseif rainbow[player] == 3 then
					if g > 0 then
						if r > 0 then
							r = r - 3
						else
							r = 0
						end
						g = g - 3
						if g < 0 then
							g = 0
						end
					else
						rainbow[player] = 4
					end
				elseif rainbow[player] == 4 then
					if b > 0 then
						b = b - 3
						if b < 0 then
							b = 0
						end
					else
						b = 0
						rainbow[player] = 0
					end
				end
				setVehicleColor(vehicle, r, g, b) ---- line 866 WARNING
			end
		end
	end
end
addEventHandler("onClientPreRender", getRootElement(), rainbowCar)

WARNING: VIP-Silver\client.lua:866: Expected positive value, got negative. This warning may be an error in future versions.

[MouNiR.Dz]

 I am not sure but i think 
EDIT : if r is more than 0 so it could be 1 or 2 *

if r > 0 then -- if r is less than 0 so for example if its 1
							r = r - 3 -- sub 3 from 1 will get the result -2 so its a negative value

i think you should use 

if r > 3 then

instead 
And yes the same for the other colors like g and b 

Edited June 18, 2022 by MouNiR.Dz

[yToPzz]

thanks