Bad sentences together. Sorry about that.
There is nothing we can do to turn a white hydrangea blue. Hence the comments about heredity.
I've got a few hydrangeas here that are supposed to be "blue". In order to turn a hydrangea blue, it's my understanding aluminum must be present in the soil and the pH has to be low enough for the plant to use the aluminum. The Oak leaf tea didn't turn mine blue because it probably didn't drop the pH around the plants enough because I didn't apply it regularly (I brew that tea for my cranberries so the hydrangeas were only getting what was left when I remembered). I also think my oak leaf tea is a lot weaker than aqh88's tea and I've had to use it before it is completely "brewed" due to severe droughts here the past few years. The Hi-Yield Soil Sulphur worked best for me when I applied it once a month starting about right now but aluminum sulfate would probably work better if you don't know whether or not you have aluminum present in your soil. I must have some aluminum because mine blued up. I was experimenting about 5 years ago after I complained to a friend that his blue hydrangeas weren't blue for me and he taught me what little I know. I was able to turn mine blue and now that I know I can, I don't bother. The pinks with a hint of blue are fine for me and I don't need to remember to do anything to them. I started creating a windbreak using pines. White pine is a real tall tree that at maturity has no lower branches. The other species of pines are intentionally planted too close together so over time their lower branches will die off leaving an open space. It was my intent to toss in acid loving plants in this open space which is why I kept some of his ornamental hydrangeas. My friend had shared this vision of beautiful blue blooms up against a back drop of the green of the pine needles and I liked his idea. Oddly enough, I changed my mind about using them in that windbreak so his hydrangeas are still planted in an alkaline area and blooming pinkish.
The oak leaf tea I use when ever I can to water a small man made bog that has Vaccinium angustifolium in it. Admittedly, when I run out I will add a T of apple cider vinegar to the water for that little bog. Should help out your blueberries but coffee grounds should too and you can always add a Tablespoon of apple cider vinegar to the water. I only grow one blueberry here and it's in with the cranberry and some other boggie type plants.
Editing to add-
Hey, there's a whole forum for hydrangeas here-
Why not ask about bluing up hydrangeas over there? Those people will probably know the answers to the mystery in their sleep!