Ok, let me tell you something that is not a secret or else I wouldn't know.
During the show, there was this Thai exhibitor selling this grooming powder that can cover the stain. It's in powder form. It was told to be a home made remedy.

Apply to the cat once a day can help removing the stain as well as preventing future stains due to the protein in the cat's tears.

Can't remember the price though. I personally think in cat fancy society, we should share all information pertaining grooming etc. For someone who attended CFA shows for the 2nd time and 1st time for International Shows, I must say the Thais really knows the trick-o-trade of grooming (In this case Persians since they were all around me).

Their cats were VERY well groom! They have the sprays, trimming and what not, I was very impressed

p.s: Note to self, more reason to get an EXO, less less less hassle to groom