How can I wash out hair dye?

As long as there are no metallic oxides in any of the dye you are fine to do that. If there are oxides in the dye then any bleach based hair color additive can react with the metal in the oxide and cause the hair shaft to be damaged and the hair to break off.

Being a mere male (with grey hair) I am not an expert but I read the product description;

"This Revlon 3D Color Technology, with a combination of specially blended dyes, conditioners and polymers, delivers natural looking, multi-tonal color from root to tip, not only boosting your hair color but also adding definition and dimensionality. The result: completely transformed, natural looking, multifaceted color and shine."

I take that to mean the product is a colour booster rather than a hair dye - in other words your hair would need to be approximately that colour to begin with.
My limited knowledge might be out of date but I always believed if a person wanted hair of a lighter colour it would have to be bleached and not dyed.

I'm assuming you are a brunette... I am too and this happens to a lot of us when it comes to dying our hair. Most brunettes have natural red or sometimes a dark blond highlights so there for when we dye it it will come out two toned. Everybody's hair has some type of natural highlight. However if you were to have blond hair and went straight to a dark brown it will actually permanently stain the hair causing any further dying is to be expected. Try dying your hair bases darker than the second tone. Next time try a cheasnut brown paying extra attention to the known areas of discoloration. Hope that helps hun

Go for normal natural blonde!

If you used a dye that has metal oxide particles in it, NO you cannot use anything that has bleach, it will react with the oxide and cause you to loose hair.

If you have a beauty supply store near you, like Sally's, purchase Roux Fanci Full Styling Mousse in one of the blonde shades to tone down the red. This product works really well and provides a wide variety of colors,

It's bad to dye it straight way, most hairdressers say that it's okay to dye it again after 3 days to a week.

Not exactly... the term "dye" causes a lot of confusion, but dye generally means making the hair darker. To make the hair lighter you must use a special bleach. Hair bleaching is permanent and cannot be rinsed away. It can be dyed back to it's original color however, but the bleach does damage to the hair. In extreme cases, where the hair was dark brown or black and is bleached to blonde, the hair becomes very thin and resembles the texture of cotton. You can lighten hair temporarily by using theatrical hairsprays. These come in every color of the rainbow including white, gray and blonde. These color sprays actually sit on the outside of the hair strand, and can be shampooed completely out after brushing the hair.