Hydrangea Blue turning increasingly red?

I have read somewhere that Hydrangeas are almost like Litmus paper and their colour tends to got towards Red when the soil is acidic and Blue when alkali.
I have just planted a new Blue Hydrangea which is very healthy and new heads are appearing but are not blue but more of a pink hue.

Is there something I can do to keep the Blue colour, perhaps a soil conditioner, if so what?

 

I used hydrangea colourant which was about £5 and worked very well on small shrubs. It didn't work on the one which is 5' by 5' though, too big and established to be affected by the chemicals I think.

 

You will be needing more acidity so adding ericaceous compost around the base, ericaceuos plant food an d a mulch of pine needles should do the trick ?
Of course I could be compltely wrong about this but one of mine under the neighbours pine treeis bright blue with next to no care from me.

 

Surely you mean less acidity?

 

You are correct in describing the colour change, Alan, but have got it the wrong way round. Blue in acidic soil, and red/pink in alkaline soil. Hence the advice you have been given is correct....