CS>yellow CS

[jessie70]

For anyone who knows:
 
I bought some Throat Rescue by Peaceful Mountain.  It is a CS spray (ionic 
silver) with peppermint oil in a concentration of greater than 35 ppm.  It is 
yellow when sprayed on white gauge. My homemade CS is not. 
 
Is this due to the addition of peppermint? 
 
Thanks, Jess