I have read that copper can discolor plants.

The technician who sprays my trees will not use copper as it is toxic to humans but I think it is safe if applied properly and the person applying it uses proper protection.

Here is an entry from the Univ. of Georgia:

Copper is toxic to fish, aquatic invertebrates, and humans. Label
directions and harvest intervals should be followed carefully.
Copper is a heavy metal and must be used in a manner that
minimizes accumulation in the soil

Coppers have the potential to burn the foliage and flowers of
many plants. To avoid this problem, do not spray prior to or
during the flowering period, or during prolonged cold, wet
weather. Refer to individual product label for plants which may
be treated.

Lime added to copper sulfate increases the effectiveness of the
copper. Phytotoxicity (burning of foliage and flowers) can occur
on many plants including the young, tender leaves of peach, plum,
rose and apple. Some sensitive plants require diluting the product
to one half strength (depending on the product used – see label) to
avoid phytotoxicity. Should not be used during cool,...(wet seasons)