When Crystals of copper sulphate are heated strongly what is the colour of the residue formed?

I guess you heat some copper sulphate (or sulfate) and see what you see.

Copper sulfate
From Wikipedia, the free encyclopedia
Copper sulfate may refer to:
Cuprous sulfate, Copper(I) sulfate, Cu2SO4
Cupric sulfate, Copper(II) sulfate, CuSO4, used as a fungicide and herbicide

Copper sulfide
From Wikipedia, the free encyclopedia
Copper sulfides (British English spelling: copper sulphide) describe a family of chemical compounds and minerals with the formula CuxSy. Both minerals and synthetic materials comprise these compounds. Some copper sulfides are economically important ores.
Prominent copper sulfide minerals include Cu2S (chalcocite) and CuS (covellite). In the mining industry, the minerals bornite or chalcopyrite, which consist of mixed copper-iron sulfides, are often referred to as "copper sulfides". In chemistry, a "binary copper sulfide" is any binary chemical compound of the elements copper and sulfur. Whatever their source, copper sulfides vary widely in composition with 0.5 ≤ Cu/S ≤ 2, including numerous non-stoichiometric compounds.

Chalcosite is dark gray to black. Covellite is indigo-blue or darker, commonly highly iridescent, brass-yellow to deep red. So whatever you see in your experiment might take a while to explain.