You could just say "yes" and see where it goes from there, if anywhere.
I think giving any further info DOES invite questioning. Just say "yes" and let them assume it is "their" god if they want to, what difference will it make?
I'm afraid that if you say "not the one you're talking about" - well, I understand what that means in the language, but it imples, and maybe subconciously reinforces, the idea that the "default" god or "standard" god is the Christian one, and you are worshipping an "alternative god"
And that is "true" in a way considering the way we use language, but then again it is not true at all
Just say "yes" and if that ends the conversation, fine. If not, and they persist asking questions, well tell them the truth proudly. Again, they will handle it or they won't, what real difference does it make?
If anything, it is a chance to teach them something.
As Shakespeare said, "a rose by any name would smell as sweet," the point being that the name of something is irrelevant. I think God is God under any name, and whether you perceive God as female or an Egyptian half-animal, you would be correct so long as you believe it. God certainly doesn't care. God probably thinks it's funny, since--by definition--God has a perfect sense of humor!
I'd recommend taking it lightly. Life is NOT serious business.
I would say, "Yes, I believe in Gods." :)