Sentence:  The video signal is amplified and then switched , in synchronism with the three ultraviolet light sources which are sequenced by the rotating mirror so that during one-twentieth of a second only one wavelength , corresponding to <WSD>red</WSD> , green , or blue , is seen . 
Meaning of the word marked with <WSD> tags:  red color or pigment; the chromatic color resembling the hue of blood