Hi,
First off, please don’t think I’m trying to patronise!
I’m a little concerned by your methodology...
Direct dye must almost always be applied to a level 9/10 with the exception of red can be a level 6. ( true red is a level 7)
I’m more concerned that House Beauty applies blue to a level 6, that will fade out very ugly! The blue will cover now, but after a few washes; Brass + Blue equals yuck!
The way direct dye works means that the base colour greatly affects the colour outcome. Levels 6-8 are naturally way too brassy for blue, even navy/denim blue.
My advice would be to get your hair done by a professional alternative colourist. The blue in the pic is actually a custom mix, I’m guessing Pulp Riot or Pravana... I can tell by the ‘smoky’ effect.
Please don’t do this yourself, without the needed professional knowledge in fashion colours and blonding, it won’t look like the picture and it’ll honestly just be a waste of your time and resource.