The morning after Frank and April decide to move to Paris, Frank leaves the house wearing a dark red tie. He wears the same tie in the office, when he tells the boys he's moving. Frank's tie is light yellow at lunch; in fact, everyone's tie is different. When he gets back to the office, his tie is red.
After John Givings' tirade to April and Frank Wheeler, Frank angrily walks from the dinner table to the opposite corner of the room. In the next shot, he is standing in the corner diagonally across of the room, sipping his drink.
Grand Central Station has only allowed electric locomotives since long before the 1950s. The train Frank takes to work is pulled by an Alco RS-3 diesel locomotive, which does not have dual diesel/electric power capability.
The masses of male commuters shown at the beginning all wear hats. In reality more than half of them would have been bareheaded. Ads by hat makers in the mid 1950s (see old Life magazine online, for example) were desperately pleading with men to go back to the custom of wearing a hat; I can also testify from personal memory that at that time in downtown Manhattan most men who worked in offices went about hatless. Had the scenes been set in winter, the men in overcoats etc, a few more head coverings would have been realistic. But not many. The mid-fifties, between the age of the hat and the age of the baseball cap, were the great age of bare-headedness.
The depiction of Grand Central station packed with uniform masses of office workers was itself unrealistic. Even during rush hour, any snapshot of the crowd there would have included a more heterogeneous crowd of people, different ages, different occupations, male and female.