So on military radios, you have the choice of transmitting secure (encryption enabled) or "in the open" (no encryption).
Back in the 80s, in Germany, when we switched from unsecure to secure, we'd call it "going green." As in, "R3B26, this is X9C12, go green." I don't know if they still use that nickname today.
My buddies and I had our own code, one we created so we could have a channel all to ourselves to goof off while driving the German countryside." We'd drop whatever frequency we were on by 10, then go secure. Between being on a different frequency than our own battalion, and being under different encryption keys than anyone else who might share this other frequency, we could be pretty sure no one else was listening in.
We called it "going orange," for exactly the reason you're thinking.
So I don't remember ever actually hearing Go Vols on those radios, but every time I heard "Go orange," I was thinking the same thing.
Go Vols! Go Big Orange!