This can range anywhere from 25 to 60 minutes, depending on the brand and type of dye that you are using. Do not go over the time recommended on the package, especially if you are lightening it.  Letting blonde dye sit in your hair longer than the recommended time won't make it lighter; it will only damage it. Pull all of your hair up into a loose bun, then cover it with a shower cap. This will help keep your surroundings clean. Do not use any shampoo. Just rinse your hair with cool to lukewarm water until the water runs clear. Next, apply some conditioner to your hair. Let it sit for 2 to 3 minutes, then rinse it out using cool or lukewarm water. Make sure that the conditioner is sulfate-free or formulated for dyed hair. You can also use the conditioner that came with your dye kit. If possible, allow your hair to air dry. If you can't do that, use a hairdryer on a low-heat setting. Some people find that letting their hair air dry partway first, then blow drying it the rest of the way works best. if it came out brassy or yellow. Get your hair wet, then apply a purple toning shampoo to it. Let the shampoo sit in your hair for the time recommended on the bottle, typically 5 to 15 minutes, then rinse it out with cool water. Dry your hair as usual.  If you added packets of hair toner into blonde hair dye, you probably won't run into this problem. It would be a good idea to wear plastic gloves for this step. Purple shampoo has a small amount of dye in it, and it can stain your hands. This is very important because your hair is still porous at this stage. If you wash it too soon, then the dye may come out or fade. Give your hair 72 hours so that the cuticles can close and absorb the hair dye.  Make sure that you use shampoo and conditioner made for dyed hair. If you can't find any, use sulfate-free shampoo and conditioner. Afterward, be sure to take proper care of your dyed hair to make the color last longer.

Summary:
Let the dye sit in your hair for the time recommended on the package. Rinse the dye with cool water, then follow-up with conditioner. Dry and style your hair as desired. Tone your hair Wait 72 hours before washing your hair with shampoo.