I'll attach these palette charts to this thread, perhaps they can be useful.
Both are for the Battlescape palette.
X-COM: UFO Defense
(https://openxcom.org/forum/index.php?action=dlattach;topic=11119.0;attach=59179)
X-COM: Terror From The Deep
(https://openxcom.org/forum/index.php?action=dlattach;topic=11119.0;attach=59180)