Dyes and color
Updated
Color is optional, it is the first thing a customer sees, and it is a variable in the burn.
Three forms
Liquid dye: easy to dose, easy to overdose, disperses readily.
Dye blocks or chips: cheap and hard to dose precisely at small batch sizes.
Powder: strongest, most economical and the messiest, and it needs proper dispersion or it speckles.
Whichever, it must be a dye made for candles. Crayons, soap colorants and food coloring all fail, and a pigment rather than a dye will clog the wick.
What dye does to the burn
Dye is a solid the wick has to draw through. Heavy loads reduce the wick's effective size and can cause clogging, a small flame and poor throw.
Which is why deeply colored candles frequently need a larger wick than the same candle undyed, and why adding color to an approved formula is a retest rather than a decoration.
The practical rule: use the least dye that gives the color you want, and test the colored version rather than the clear one.
Color on a shelf
Color is what sells a candle at two meters, before anybody reads a label or smells anything.
It also reads as a scent promise. A pale green candle that smells of vanilla confuses people, and that confusion costs a sale more often than a bad color does.
Uncolored is a legitimate and increasingly common position, and it removes a variable from every test.
Matching a color
Judge on a cured, set candle in daylight, never in the melt pot: liquid wax is always darker than the solid, often dramatically.
Keep a swatch candle of every approved color and match new batches against it. Dye lots vary and a shade drift is very visible when two candles sit together on a shelf.