Go get yourself some "oxyclean" powder in the laundry isle.
pour about an 1/2-ounce of nearly boiling water on the area. then saturate a white cotton terry towel rag with same, and squeeze it out until damp but not dripping, fold it into doubled, third or quarters.
Take about 4 scoops worth and put it in a pile on top of the stain, cover it with the towel, put a layer of saran wrap over top of the towel, then weight it (the poltice) down with a non-reactive layer (like a rubbermaid dish pan, with something heavy set inside like a stack of canned goods). Leave it sit for at least 4 hours.
Return and remove the weight, plastic, towel, and sprinkle the powder with more very hot water (135-140 degrees F) and stir same with a wooden stick, create a paste, and repeat covering with hot damp towel, plastic and weight for another 4 hours. REturn and wipe up same. see if blueberry stain has reduced, if not, create a concentrated liquid with fresh oxyclean lots disolved in small amount of HOT water, and apply immediatey.
If still doesn't work, next after rinsing completely and drying completely, next time around try a solution of 50% regular, unscented CLOROX bleach and water, allowing to pool on the surface and to remain pooled (may need to make a "dam" first try some laytex kitchen caulk 3 days in advance apply a "ring around the stain and let it cure") for 2 hours, then mop up and rinse completely.
Oxyclean method should work, if not the bleach method should. When stain is removed, and entire surface is well cleaned, suggest you SEAL the grout, its obviously past due for same. (use special cleaner/prep recommended by manufacturer of the sealer first).
If all else fails, use a grout saw, remove grout in the effected area, re-grout, then seal grout.
Be sure to use a grout sealer that is rated for kitchen surfaces/food contact or "food preparation surfaces. One that is only rated for "incidental food contact" is not sufficiently SAFE for kitchen countertops.