I have been some of the criticism that is levelled at the colours of this. But the thing is the reason why filmmakers love gunmetal is because red, especially the extreme colours, are difficult to photograph without an insane amount of light.
My original idea was to use same color scheme as in the movie. I´ve decided to keep Thundercracker as original flat grey realistic fighter. Starscream have got just some red details, and Skywarp is the only who keep his original toy scheme because a black and steel fighter is really appealing on a movie.