How do I turn my Hydrangea blue?

Can other Hydrangea flowers be coaxed into changing color through pH manipulation?

In alkaline soil (pH over 7) the mopheads (H. macrophylla) can be coaxed toward blue with the addition of acidifying agents like aluminum sulfate (fast acting/short-lived) or sulphur (slow to act/but stable and long-lived).

Only cultivars of Hydrangea macrophylla (the mopheads) change color based on soil pH.