Spielberg wanted his war film to be gritty, dark and bleak. That meant keeping colors cool and dark. War isn't a happy place to be, and the legendary director thought that a bright color palette would send the wrong message, so his original draft of the film looked deliberately washed out.
Unfortunately, his vision didn't play well with TV audiences. It was fine on the big screen in the cinema, where it was considered to be part of the film's experience, but didn't look as strong thematically on television. When the movie premiered on television, two separate cable firms contacted the studio to report that viewers thought the colors looked so bad that there must be a fault with the film; and so, the whole color scheme was re-done for future broadcasts. There's no accounting for taste!