data Color = Red | Green | Blue 

The data Constructor is Red, Green, Blue
:t Red => Red::Color    = function with return type Color
:t Green => Green::Color = function with return type Color
:t Color => Error, Color has no type
:kind Color => Color::*  -- Color is a kind 

data Color = RGB Int Int Int

RGB is data Constructor
RGB is a function RGB::Int->Int->Int
:kind Color - Color is kind

data Color a = Red a | Green a

Color is type Constructor

-- list
Data List a = [] | a:[a]

-- Binary Tree
Data Tree a = Empty | Node a (Tree a) (Tree a)

-- Java Binary Tree
Node {
    int a
    Node left;
    Node right;
}