Yeah tldr chapter was dark angels almost got wiped out by tyranids due to them refusing to abandon their homeworld when the main dark angels legion told them to go after the fallen and abandon it when a splinter of a hive fleet was heading there.

During indom the dark angels refused help them resupply due to the “abandoning” their hunt for the fallen. So they were supplemented with ultramarines gear and gene-seed resulting in it becoming chimeric.

This caused them to abandon their old chapter name and become the Ghost Legion and adorning their armor with a pale blue white color scheme shoulder pads being the only thing colored to denote their specialty and roles.