Q: Can most developers be used with other products or just the product it was intended for? Example: Can a Redken developer be used with a Wella toner?
A: Most hair-color developers follow a standardized formula, and in a pinch, I would say you could use your Wella toner with your Redken developer without fear.
However, many companies add ingredients to their developer formulas that are designed to maximize the effects of their color portions of the mixture. In these cases, using a specific
color formula with a developer of a different manufacturer (or even from a different product line of the same manufacturer) can mean you won’t get the same results as if you used the developer that was intended for use with it.
Of course, most companies have their basic colors and developer formulas, and barring specific product formulations, you shouldn’t worry overmuch if you need to mix manufacturers in a
pinch. However, when in doubt, check your product literature. Any precautions or preclusions on use of the color or developer with other product brands should be listed.