Which toner you should use really depends firstly on your hair's current level and degree of brassiness. It also depends on your expectations in terms of blonde transformation.
The chart above should help you make an informed choice.
The rules are as follows:
If your hair is very brassy, orange with brown. then it's basically level 6 or even level 5. You need to lift first using a good quality bleach, then tone with and of Ugly Duckling's intense toners, either intense pearl or intense silver.
If your hair is lighter than that, say level 7 or level 8, you can get away with just using the intense toners with 20 Vol. You will get rid of most of the brassiness that way.
If your hair is yellow only, in other words at a level 9 or level 10. In that case use Ugly Duckling's no-lift toners, either pearl or silver blonde.
For quick gloss toning rather than a major blonde transformation, then use Ugly Duckling's new Ammonia Free Liquid toners.
To learn more, go here: https://www.uglyducklingcolor.com/content
