jason.p is right about testing the raw substances - although (unless you have some of each to compare) it isn't always easy to tell 'yellowish' from 'reddish' with a standard human eyeball.
Apparently you make a very concentrated solution of the KCl and dip a wire loop into it - should then burn very bright lilac in a bunsen burner flame ...
Toby & Dave
Strictly speaking KCl and NaCl are both salts, along with a wide range of other compunds. NaCl however is known as "common salt" and is the variety they put on your fish & chips.