exxdee

function zigzag(X) return math.acos(math.cos(X*math.pi))/math.pi end
    counter = 0

while wait() do
    for i,v in next, game:GetService('CoreGui'):GetChildren() do
        if v.Name == "JailFixer" then
            for i,a in next, v:GetChildren()
                if a.Name = "Underline" then
                     a.BackgroundColor3 = Color3.fromHSV(zigzag(counter),1,1)
                     counter = counter + 0.001
                end
            end
        end
    end
end