Tear stains present as discolored hair under and/or around a dog's eyes. The hair may develop a pink, red, rust, or brown tinge. Sometimes the texture of the hairs will feel dry and a bit 'crunchy' similar to straw. But, even if the hairs are soft, any discoloration like this is still indeed stains.
Something seen very commonly with Maltese owners is that they will have a Maltese puppy that is a pure, snow white without any color around the eyes at all. Then, as the pup matures, pink or brown hairs will 'grow in'. When this happens, owners may think that this is some sort of natural coloring. It is not.
Maltese do not have the genes to produce rust, brown, or dark pink hairs. This breed can
have lemon or tan; however, if this is there it is almost always present on the ears.
Therefore, any coloring that you see as your Maltese grows older is due to unnatural staining. But, not to worry; this can be resolved relatively easily.