How to wire a light with two sets of wires

Question

How do I wire a light fixture here? There is a junction box above the bathroom vanity. I want to add a vanity light here. There are two sets of wires in the j-box: One which has black and white, and the other has black, white, and red.

The bathroom has 3 switches: One controls the overhead light above the vanity (which I would like to tie this new fixture into), one controls the light above the shower, and one for the fan. When the switch (for the overhead light) is off, I get 0 V between red and white, 125 V between red and black, and 125 V between black and white. When the switch is on, I get 125 V between red and white, 0 V between red and black, and 125 V between black and white.

I believe I would wire the two wires from the fixture into the red and white, but just want to get some confirmation. Thanks!

Answer 1

Based on your description and the picture (thank you) the red wire is the hot switched loop to control your light. Connect your black wire from the light to the red wire in the box, the white to the white and the green from the light to the bare ground I see lurking in the back of the box.
You should be good to go.