I can't figure out the science to why the top brake light is red on some models and white on others, does anyone know?

My 04 3.0 had a clear one and my 05 4.8is has a red one. I would have thought they would have made them all clearer newer and it seems that some model years have clear ones and some don't... anyone know the deal on that? I have always been curious..

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Vehicles:

1. 2005 4.8is X5 Sapphire Black Metallic/Black Leather, fully loaded (Nav, Comfort Seats, Rear Climate, Sliding Load Floor, Heated Front and Rear Seats, Aux In)
2. 2004 3.0i X5 Jet Black/Black Leather (Lemoned)
3. 1999 Saab 9-5 Turbo (Trade In/Retired)


My Custom X Page (Pics of my 4.8is)