Hmm... email me a photo at [email protected]
The underlying latex color of Bongo is blue, not black, so that's not it.
Is the black paint from his mouth transferring to the upper lip? It's possible but very unlikely this soon.
Are you having a chemical reaction causing dark green finger marks to stain the latex? Copper coins can cause this if you don't wash your hands. For example if a cashier (who handles pennies all day) doesn't wash their hands and handles latex the copper can affect latex.
Looking forward to helping you buy email.