After exporting a photo, I'm noticing a major difference in colors between the photo I've exported (now being viewed outside of Lightroom) and the photo as it looked in Lightroom. I'm not sure if this is a color space issue or a calibration issue or something else entirely. My camera (Nikon D750) is set to sRGB, as are the exports. Below is a screen shot of the exported photo (on left) and as it shows in the Lightroom development panel (on right). What is causing this, and how can I fix it?
It could be that the application you are using to view the photo outside of Lightroom is not color managed.
What application is it?
Also, is your monitor calibrated?
I'm not sure if this is a color space issue or a calibration issue or something else entirely.
You seem to be using the Windows Photos App, which is not color managed, and will not display correct colors.
Lightroom is color managed, and will display correct colors, as long as the monitor profile is correct.
This difference in color is more pronounced if you have wide gamut monitor, in which case you have to use only color managed applications to view your work.
Bridge and Irfanview are both free and color managed (you have to enable color management under Settings in Irfanview).
On Windows 10, the Windows Photo Viewer is apparently still color managed, but it's hidden somewhere. Do a search for it.
A paid option is the latest version of ACDSee (20).
My camera (Nikon D750) is set to sRGB
The color space you set in the camera only affects jpgs (and the jpg embedded in the raw files), if you shoot raw, it doesn't matter which color space you choose.