Why did the author say "the grey or multicolored lights touching their faces, but never really touching them"?

Bradbury is talking about the flickering lights of a television set dancing across the faces of people in their homes doing nothing but watching endless channels of television.  The entire description reads,

Everything went on in the tomblike houses at night now, he thought, continuing his fancy.   The tombs, ill-lit by television light, where the people sat like the dead, the gray or multicolored lights touching their faces, but never really touching them.

Bradbury compares...

Bradbury is talking about the flickering lights of a television set dancing across the faces of people in their homes doing nothing but watching endless channels of television.  The entire description reads,

Everything went on in the tomblike houses at night now, he thought, continuing his fancy.   The tombs, ill-lit by television light, where the people sat like the dead, the gray or multicolored lights touching their faces, but never really touching them.

Bradbury compares the people of the town to the dead and their homes to tombs because of their obsession with watching television. The society no longer needs books or magazines because television has taken over their lives. None of the programs are probably worth watching and are for entertainment only; therefore, no knowledge is sinking into the brains of the citizens.  They shut themselves up in their homes and are hypnotized by what television can give them, an escape from their own lives. Unlike Leonard Mead who takes nightly walks, the rest of the city spends their nights in their tomb-like homes and merely exist not learning or growing or accomplishing anything in life.

The key to understanding the quote is to analyze the use of the word, “touching.”  The light from the television set touches the viewers physically, but nothing on television ever touches them emotionally.  They are the “watching dead” or zombies created by the television age.