Ooooher you're messing with a great force of nature here man...
If a root was human it would be a massively intelligent life source, the filtration system it utilises has never been worked out properly, even by top biologists, simply because its so complex! Somehow it knows that this pigment is there and holds it back, it dyes the roots nicely though! To trick a plants root zone into releasing this dye into the plant is a whole new story...
I once flushed a shit strain with a sweet, blueberry food flavouring for a week or 10 days to enhance its bag appeal, res stunk of berry, house stunk of berry even my clothes and undies stunk of berries but weed stunk and tasted of weed... my brother a very clever fella worked in fragrance and flavours all his life, terpenes, oils, hormones, auxins, esters, chems, compounds you name it. He tried introducing neat flavour compounds, terps, oils etc to his crop all the time, it never worked and somewhere on here I read his ramblings regarding it. In fact reading through his grow diary was a revelation as to how far he took his experiments, like some some mad bastard in a white coat!!!
Chop a stem and stick it in blue food dye and for a week it will take up the colour, we did this at school and a bit more of a complex experiment at uni. But it only gets the leaves and white flowers, it'll be dead before it gets into the flower bud of MJ imo. Chlorophyll as a pigment is like a colour defence system it don't like other colours coming through them roots man, don't get your hopes up and try it if its of interest to you... Plus I like shit like that
mainly not doing this though save maybe a 1/4-1/2 oz from my 15oz crop