I really don’t think it matters. I’ve used tea lights before when that was all I had, but I wanted to try to do the ritual the way it was written, and still garnered results.
As far as using candles or not- I’ve used them probably 25% of the time when doing djinn rituals. I can’t visualize a black candle, but I can imagine the texture of the wax, the sound etc- so most of the time I use imaginary tools that I can’t even see in my imagination- and I get results probably 80% of the time with djinn, at least.
Sorry guys, I’m on a bit of a hiatus.