When you dye your hair a darker color temporarily, does it really wash out??

When you dye your hair a darker color temporarily, does it really wash out???
Slowly but surely it lightens up. Give it about a week or two

Temporary color don't contain ammonia. They coat the surface of the hair and usually wash out within two or three shampoos. However, this may not be the case for blonde hair or chemically treated hair. Blonde or chemically treated hair can be extremely porous and may absorb the color like a sponge, and it may take longer to wash out.

Well I am a Natural dirty blonde, but most of my hair is really dark blonde anyway so I was thinking about temporarily dyeing it brown to see if I like it.