The Fighting Fourth
The Fourth does not use the standard Marik Militia paint scheme. Instead, the 'Mechs of the Fourth use a blue-and-white pattern for parade colors with their insignia, a 'Mech stepping on a tank, displayed prominently on the chest.
Per FM:Free Worlds League, page 56.
Each 'Mech displays the Marik Militia crest - a stylized Marik Eagle on a red and blue background - on its left arm or weapons pod. The 'Mechs of the Fourth display their insignia, a mech stepping on a tank, prominently on the chest. Per FM: Free Worlds League, pages 53 and 56.