I don’t advise black crayons - tried that. They are not dyed as much as pigmented. Pigment is basically tiny particles, they sink to the bottom of the candle, and if your candle was an upside down pour, are positioned perfectly to clog up the wick and kill the flame.
You can order supplies online. Dye chips are cheap and easy to use. I like Pringles cans as free disposable molds. For a Pringles can with parafin wax at abou 140 melt point, use a natural square braided wick size #2. You can make a wick hole in the bottom, do get wick putty to seal it, reinforce with duck tape and pour as cool as you can on a tray, you don’t want dyed wax staining your kitchen floor.
I’ve been making candles for 30 years, I make all my own and can probably help with any technical questions you have it you go that route. Feel free to PM or post here
I have another post with some details for candle making from not that long ago here as well.