Hydrangea Colouring

Some time ago I had a question answered about how to keep a Blue Hydrangea Blue and was directed to Hydrangea Colourant.
Now I have a follow up question.
Now that the growing season is past and the flower heads on the Hydrangea are wilting should I continue to water the plants with the colouring agent or wait until next year when the buds first start showing?

 

Agreed. Did it work for you? I used it from about May til July, not often, and it worked for me.

 

Not really as I think I was too late in applying it. We will see next year whether it works.

 

Here were my results but they are only small shrubs.


It didn't work on this one though, too established/I didn't apply enough...

 

Just a random thought...

Hydrangeas can be red, pink, blue, white, and variants of those colours.

Blue hydrangeas will turn pink if the soil is alkaline. Hence the special feed to keep them 'true blue'. However, if you have a pink hydrangea, no amount of acidifying the soil will make it flower blue! Do you know that the large pink-flowering hydrangea is a blue?