you need to give it an iron sequestrine feed . you can buy it at the garden centre. just tell them about your blue hydrangea going red.

You can also get a special feed for the purpose, or alternatively I believe you can use Epsom salts.

Some blue hydrangeas 'fade' to red as the flowers die off. Do you know the specific variety?

Epsom salts is for the production of chlorophyll as it contains magnesium.

Oops, asleep again! should have said flowers of sulphur.

Thanks everybody for the comments back, sorry for the late response.

did you treat it and did it work?

I put some copper pipes and limes around it. The rest red one started to fade off and one start to bloom a bit blue so it seem to work. Start again next year. Thanks