crayons

I found some old crayons from when I was young and figure I can melt them down to pass onto the next generation. my niece is 16 months old, so I know a larger chunky shape is needed. Would a Wilton candy mold be big enough? The molds I have I use for embeds, would lingering FO residue transfer...

I've heard that some candle making hobbyists use wax crayons to color wax for candles. What do you think about it? Are these colored with pigment dyes or wax soluble dyes? Considering that pack of crayons costs 0,5$, that would be a cheap dye.