Why is this Flag script not working?

So this script is supposed to make a billboard GUI in a part in the flag say what team owns the flag. However, it's not doing anything. Output did give me something, I'll post it after I post the script.

Can someone please help me? Here's the script:

repeat 
wait()
until script.Parent:findFirstChild("CurrentOwner")

while true do
    local player = script.Parent.Name
    if script.Parent.CurrentOwner.Value == BrickColor.new("Bright blue") then
        player.GUI.Who.Text = "China"
    end
    wait(0.1)
end

Output: Workspace.Captureable Flag.Detect:8: attempt to index field 'GUI' (a nil value)