I purchased one L'oreal Hair colour. In the instructions, the advised the creame colour add with the developer, and the mixture will use for hair. It is OK. My doubt is how many time/days we can keep this mixture for future use ? And how we keep the mixture safely ? Or We make the mixture for each applications ?

If the dye is mixed, you should not keep dye mixtures for future use. First of all, if you keep developed dye capped, it runs the risk of exploding--or even catching fire--as the ammonia expands. Second, the dye should be used before it finishes developing; as it's exposed to the air it oxidizes and loses potency.

If the dye parts have not been mixed, it is safe to keep them indefinitely for future use, but ONLY if they have not been mixed.