1.  Purple is a color sensation produced by simultaneous stimulation of blue and red color receptors.  If a colorblind person lacks blue-absorbing pigments, then the color purple would appear to be the same as the color:

Green

Red

Blue

Yellow

2.  If a man lacked red-absorbing pigments (see Figure 1), he would be unable to discriminate between:

Red and Blue

Green and Purple

Red and Green

Blue and Purple