Error with userdata value?

Why isn't this working? I always get this error : attempt to perform arithmetic on field 'ImageColor3' (a userdata value)

I don't get it..?

color = script.Parent

while wait() do
    local i = 0
    repeat
        wait(0.2)
        i = i + 1
        script.Parent.ImageColor3 = script.Parent.ImageColor3 + Color3.new(0,0,0+i)
        if i == 10 then break end
    until i == 10
    wait()
    local ii = 10
    repeat
        wait(0.2)
        ii = ii - 1
        script.Parent.ImageColor3 = script.Parent.ImageColor3 + Color3.new(0,0,0+i)
        if ii == 0 then break end
    until ii == 0
end