Thanks for your reply, YuengLinger. I will read those articles. It doesn't have to be perfect, just "ballpark." The problem I get into is that many of the indoor venues where I shoot have a mix of tungsten, and multi-temperature fluorescent and LED lighting (so you can never really get it "perfectly" balanced). I am wanting to avoid "testing" multiple gels until I get the best one. It would be nice if I could just see a dominant degrees Kelvin displayed in the camera and just put the appropriate gel on.
Couldn't you find a variety of indoor lighting to try the gels and get comfortable before an actual shoot? Offices, schools, your home, your garage or a parking garage, etc. Basically there's incandescent, halogen, fluorescent (including CFL) and LED. LED, so popular now in canned lighting (recessed in ceilings), as you said, can be anywhere from very warm to quite cool. The point is, I think with a little testing on your own, well before a shoot, you can learn to get very close and know which of the filter gels will serve you best. You can look at how the light plays on the back of your hand, get a sense of the temp in the room, look at the lights themselves, and decide which gel to go with.
And some events just work best with the mix of lighting, not trying to get everything a "proper" skin tone, but catching the character of the lighting as it actually played on faces.
Black and white is one resort!
Then there is another factor. If the walls and/or ceiling of the venue are close to white, and you use bounce flash, the flash is going to dominate. In a way, this can make life easy, as your flash will help produce pleasing skin tones regardless of the lighting. However, if you have to bounce off colored walls, that's another challenge, one you'd want to work out early, before the event starts.
At some point, changing gels during event photography is going to result in lost precious moments. If a certain lighting is dominant, ok, but what if each room has something different? Maybe "fixing" things in post isn't ideal, but events can be so quick, so hectic, and often unpredictable.
It can be a lot of fun learning by playing without the pressure of an actual event. Have a friend stand in.