Hey mate,
its mostly in the genetic.
You can enhance the colorisation through swings or extreme values in temperature, ph or light. But that wont be good for your plant and when the genetic component for colorisation is completly missing in your plant you cant do anything sadly to make it color. Its just not possible sometimes. Maybe you will see slight colorisation in the maturing.
Your plant looks more than nice anyway.
Keep it up and Happy Growing!👌