Find primary source materials on the battle in CAO: https://archives.library.wcsu.edu/caoSearch/catalog?q=%22Cold+harbor%22&search_field=all_fields. The battle was a major loss for the Union in terms of casualties, but marked the end of the Confederate army’s ability to maneuver in their defense of Richmond which fell 9 months later. Defeat of the Confederate states’ attempt to preserve slavery is commemorated on the Juneteenth holiday (at times it was celebrated as Emancipation Day) – materials in the CAO regarding Juneteenth may be found here: https://archives.library.wcsu.edu/caoSearch/catalog?search_field=all_fields&q=Juneteenth.
Surprisingly, a century ago, a representative from the 11th Connecticut returned a flag, captured in the battle to representatives from the Louisiana regiment from whom it had been taken.
A complicated story: Captured Flag Is Returned from New Britain Daily Herald, Wednesday, June 10, 1925 (Chronicling America). Just two months later, 30,000 white supremacist in the KKK marched on Washington.
Connecticut's Archives Online