Can't you just use blue food colouring?
One easy source is - surprisingly, perhaps - sunflower seeds. Soak some hulled seeds in water and check it out. That's your anthocyanins right there, and for mere pennies.
Beetroot's colour comes from a different class of compounds, the betacyanins. These would most likely turn yellow in contact with freebase DMT as the pKₐ for them turning completely blue is above 12 (based on practical experimentation).
Red cabbage is of course the obvious classic for anthocyanin pigments, although a CWE from sunflower seeds is arguably the easiest approach.
This latter paper led to a minor rabbit hole in that sunflower seeds, aren't really seeds - they're in fact not even achenes either, but rather
cypselae on account of the inferior ovary. Extra points if you've even heard of a cypsela before (I hadn't, so maybe that's why the botanists didn't want to talk to me. The more you know…).
Some useful details here:
Their early work on the achenes:
Expect around 1% anthocyanins from a sunflower cypselae extraction using formic acid, although this may depend on the variety of sunflower:
HanMYB1 was found to play positive roles in the modulation of anthocyanins metabolism based on the integrative analysis of different color cultivars and the related molecular genetic analyses. As a high value ornamental and edible crop with various ...
www.ncbi.nlm.nih.gov
Epigenetic techniques might help yield higher anthocyanin levels, although it probably makes more sense to use the pericarps if you're breeding sunflowers for the purpose of, er, dyeing your DMT blue.
