How to install vanity light - wall box has 2 white, 2 red, 2 black, 2 ground wires
The red wires are indeed unconnected
If you look at the red wire in the cable from the switch box headed to the vanity light and trace it, it, along with the red wires in some of the other cables, is capped off by itself as an unused &quot;spare&quot; wire, in accordance with what your electrician is saying.  So, I would simply cap off both red wires in the vanity light box by themselves then connect all blacks together, all whites together, and all grounds together.  You can then mount the fixture, turn the breaker back on, and enjoy your new vanity light!