stationScreens.lua

monL = peripheral.wrap("left")
monR = peripheral.wrap("right")
rednet.open("top")
local station = "OAK HILL"
local cartMSG = "INCOMING CART"

function setDefault(mon)
    mon.setBackgroundColor(colors.blue)
    mon.clear()
    mon.setTextScale(4)
    mon.setTextColor(colors.white)
    mon.setCursorPos(5,1)
    mon.write(station)
end

function receiveMSG(mon)
    id, message = rednet.receive(3)
    if message == "incoming_cart" then
        mon.setBackgroundColor(colors.red)
        mon.clear()
        mon.setCursorPos(2,1)
        mon.write(cartMSG)
        sleep(15)
    else
        sleep(1)
    end
    setDefault(mon)
end

setDefault(monL)
setDefault(monR)

while true do
    receiveMSG(monL)
end