@TheGIT13
I'm not sure what you are asking. Do you mean the background used when cards are recorded ??
If so, the background (green / blue) is used as a chroma-key so that during post processing, the background color can be changed to transparancy. The color may be selected based on what the model was wearing. If the model is wearing blue, then using a blue chroma-key would make those items also transparent, so you would use green.
If this is not what you were asking ... more detail is needed.