If a translucent blue copper sulfate solution is mixed with another solution and changes to a translucent lighter blue color does that mean a physical change occurred or a chemical change?

The answer would depend on the color of the solution added. If the solution is clear, the lighter blue color could be caused by dilution of the copper sulfate.

Chemical reaction indicated by a change in color (blue to red), sedimentation, gas/bubbles, odor, and temperature changes. The lighter color (blue to lighter blue) is more likely to be physical changes than chemical