The yellowish part is illuminated because Ranger Angela (or somebody) was shining a flashlight on it.
"Crystal Ice Cave contains some of the most spectacular ice formations among Lava Beds’ many caves. Because of the sensitive nature of this cave's formations and air flow, it is open to park visitors on small ranger-guided tours only during winter months."
This is from the Lava Beds National Monument's spiel. They limits access to the cave to six people per week and only during the Winter. More people than that entering the cave will raise the temperature and melt the ice. I will be posting some really cool photos of this cave this week so stay tuned.
More Crystal Ice Cave: