Sentinel Major
From Halopedia, the Halo wiki
Summary
Sentinel Majors are the same basic design as the Sentinel, with two notable exceptions. One is the gold-colored armor plating replacing the normal silver-colored armor plating. It is unknown whether this is a difference in color or a different armor alloy altogether. The second difference is that the Sentinel Majors are armed with Advanced Sentinel Beams that fire blue-colored lasers instead of the weaker orange-colored beams that normal Sentinels use. The Sentinel Major is also equipped with energy shielding that can absorb more damage than a normal Sentinel.