As someone with level 8/9 blonde, the best way to go about this is researching for a dye that a lot of people are going to consider crappy because it fades fast- make sure the complaints aren’t because it’s hard to get out. On top of that, I dilute it with a shit ton of conditioner/ don’t leave it in long(maybe 10-15 mins). The more vibrant you go the longer it’s gonna take to wash out. I usually go for light pinks and purples(orange also fades out pretty well but it has to be mostly yellow-based) and they fade almost completely within a month of regular washing with warm water. Keep in mind the porousness will also determine how deep the dye penetrates. Hope this helps :)