Nissan's TPMS Sensors Color Codes?

[minionite9]

Does anyone know why Nissan has different colored TPMS sensors? Here's some examples.

http://thumbs4.ebaystatic.com/d/l225/m/mvOUnS5Yr2mB0baHA9zlCag.jpg

https://encrypted-tbn0.gstatic.com/images?q=tbn:ANd9GcRo7Q84BRIszcaUUQmGUtxL9LYGX22zz P9Xnw4ghQopEFQknFD8

https://encrypted-tbn3.gstatic.com/images?q=tbn:ANd9GcQb3Vxox-1v-O6EHkJNBrtdNOmi1veRuir4wb6iWqMLoo7k9i7pWA

https://encrypted-tbn0.gstatic.com/images?q=tbn:ANd9GcSsj-mAo1vPgBn-j9JFq8en-e4iLJ9540h5keTVuEdwGUHH-3b0dw

[TPMS Guru]

The casing is just a different color. They all operate the same and there are not any differences between the sensors.