There are several companies that sell the exact paint in an aerosol can color to match, you need to know the model or code and it even has the hardner built in. You can take the speaker outside, lightly sand with a 400 gtit wet dry, tack cloth if off, mask it and paint it with several lite coats. You can even color sand and polish it out to blend it in perfectly.
Automotivetouchup.com Touch Up Paint, Aerosol Spray Paint and Touchup Paint Accessories | AutomotiveTouchup | 888-710-5192
take a look they have many types of products etc. I used their stuff on my $100, 000 cuda and you can never see where I did the work on her.
You can even get the clear coat if needed as well.
This is the real deal not a auto store paint can, but the good stuff!
Comes in full Acrylic Enamel and Lacquers.
PS make sure you are in a good dust free location, no wind and have a respirator on too
good luck it is a fairly easy process.
You can call and talk to them as well.