theres really no way to do so because atmosphere works via the skybox in the game, so you;d have to change the skybox to a red one. But if you must have a script for tweening it here it is
local TS = game:GetService("TweenService")
local Object = game.Lighting:FindFirstChildWhichIsA("Atmosphere") or Instance.new("Atmosphere")
Object.Parent = game.Lighting
local Goals = {
Color = Color3.fromRGB(199, 0, 0),
Decay = Color3.fromRGB(92,0,0),
Glare = 10,
Haze = 10
}
local Info = TweenInfo.new(10, Enum.EasingStyle.Quad, Enum.EasingDirection.Out, 0, false, 2)
local Tween = TS:Create(Object, Info, Goals)
Tween:Play()