Kari Blue is about the 'bluest' lavender I've ever grown. Nice enough waterlily with fair number of blooms. Lilac Time, if you get the right version of it, also has a bluish tone on a rich lavender. Don't fall for the photoshopped garish blue dahlias you see advertised- they are misleading.

I've never grown Worton Blue Streak, but have read that it has that same slight blue tone.

Thank you for the suggestions. Advertisements are very misleading which is why I asked for recommendations.
They will be for my ds grave site as that was her favorite color. This year we found the perfect colored iris, but alas, the bloom time was short.

For a gravesite, I wonder if you'd be better to stay with a lower growing dahlia like Worton Blue Streak then(3.5 ft tall.) My Kari Blues were always very tall- 4-6'- which isn't unusual for my beds. Lilac Time is 4 ft for me.

Here is a link that might be useful: Link to Lilac Time's bluish tone

Just saw your Unforgettable in the gallery. I think I must get that one to go along with whatever purple one we decide on. Your others are stunning too, but the name is perfect.

Worton Blue streak is the closest I have come to blue so far.

Unforgettable is one dahlia I never want to be without. It would be lovely with any purple you chose.