THanks, I googled "hydrangea" and found the answer. I copied the info: "In acid soil the blooms will be blue, pink flowers in alkaline soil, and white in neutral. The flower colors may be controlled by adding aluminum sulfate to the soil prior to budding to produce or keep blue flowers; or by liming or adding quantities of superphosphate to the soil to produce the pink ones." I'd like to add my 2-cents worth to say that the drought has adversely affected things in a big way too.

I tablespoon of aluminum sulphate in one Gallon of water...make sure all the crystals are dissolved... before the alum. sulphate application, make sure you water the hydrangea plant well..it is ok if it is dripping wet.. pour the al. sulphate solution right at the base of the plant, do not let any of the solution to touch the foliage or the leaves will get burn spots.. one gallon solution is enough for a mature hydrangea plant (3' X 3').. let the solution sit in the soil for an hr and water the plant lightly and briefly to wash off any extra solution sitting in the soil that could burn the roots... you should not apply the solution more than once every two weeks...you can apply two applications in a month and not risking to kill the plant...much more often than that, i dont know, but i won't reco it.. btw - the pink blooms already blooming now WILL NOT chg to blue even after the al. suphate solution.. the sulphates will make the soil more acidic and future bloom colors will chg accordingly.. so if you have a rebloomer like endless summer now and it is beginning to show the pink blooms, the sulphate application will not chg the pink blooms now..but the new blooms later in the season will chg to blue if the pH is low enough// if you dont have a rebloomer and all the buds are set already, an al. sulphate application would not chg the color for the blooms this season.. for me - I don't do al. sulphate applications much because it does poison the soil to a certain degree - if you have a Rhodi or Azalea nearby, they may not appreciate the extra aluminum in the soil...whenever I do the sulphate application, i do one in spring - when the flowerbuds are forming - april in that case...and another one in July for the later blooms...twice is enough for me to keep my endless summer to bloom in a brilliant blue color... have fun..

Better timing may have been to apply in earliest Spring just as your hydrangea was breaking dormancy - it isn't possible to change flower color within a couple of weeks; if you are in an area with alkaline soil and water it could take months (you might see results of your efforts the next growing season) or may not be possible at all. Don't add more now...an excess of aluminum sulfate can be toxic to your shrub. Here is a link that might be useful: Earlier discussion aluminum sulfate

From the shape and configuration of the sepals, it looks a bit like 'Fuji Waterfall' (syn. 'Fujiotaki'), which Dirr describes as a "loosely configured mophead". He goes on to describe the flower color as white suffused with blue in acid soils or pink in more neutral soils. Coloring of mature flowerheads can be rather variable depending on climate, amount of sunlight and watering conditions, but the greening followed by reddish tones is not uncommon on a lot of different hydrangeas. A photo of the shrub in blossom during the growing season might be more helpful. And there seems to be some confusion in the labeling of plants with this name - often 'Fuji Waterfall' is described as a lacecap with a cluster of fertile flowers surrounded by the cascading sterile ones. Dirr's photo shows only a loose cascading mass of sterile florets but even fully mophead varieties tend to hide a few fertile florets here and there. I'm not at all convinced that there are not at least two plants going by this name, one also referred to as 'Fireworks' ('Hanabi') or sometimes 'Shooting Star'. These names tend to be used interchangeably but there are hydrangea authorities (Dirr and Barry Yinger among them) who are firm that these are distinct plants.