The coloured foam enables the microphone to be placed in the frame and closer to the talent for optimal sound quality. Chroma key compositing can then be used to remove the microphone from the image.
Rode WS-Chroma Chroma Key Windshields
WS-Chroma is a set of two foam windshields for the VideoMic NTG coloured blue and green, making them suitable for chroma keying.