It says "Bordeaux mixture" on the pack.
It says it contains copper sulphate BUT the powder inside and the
deposit left on the plants is white. I also thought it would be blue.
Perhaps someone can explain!

I vaguely recall my first ever chemistry lesson at secondary school...

"Copper sulphate crystals were placed in a test tube and heated over a
bunsen flame. A crackling sound was heard and steam was seen escaping.
A white substance remained in the test tube."

The white stuff was "anhydrous copper sulphate", i.e. with all the water
removed...