These rear parcel shelf speakers are notorious for becoming brittle and cracking. I once dropped one of these covers and it shattered like glass.
I've had a crack in one of mine for ages and so I finally decided to do something about it. Palomino covers are very difficult to find and when you do find a set, they often cost more than they're worth.
Instead I went a different route. I had a good chap send me a pair of black covers from a breakers yard and I decided to paint them palomino.
With a recommendation from someone who knows about paint I bought this aerosol palomino paint from ebay. Its made by "SEM" and I bought it from a company called Eastwood. Here is the ebay link.
I practised on my broken cover a few times until I got it right. Although you're meant to use a plastic prep and plastic primer, I don't recommend it. My experience wasn't very good when using these products. It just seemed to flake off very easily.
I simply lightly scuffed the plastic with 600 grit paper, and perhaps 200 grit on the grill and sprayed it straight with colour. This produced a very tough finish. I've deliberately scratched at it quite vigorously and it shows no signs of deterioration.
The colour match, although looks perfect to the untrained eye, is actually not an exact match to Mercedes palomino. Mercedes uses a slightly darker shade of palomino on all the plastic trim pieces. Plastic trim in a palomino w126 is not the same colour used on the seats.
The aerosol is actually an even better match to the seats. And although advertised to be used on leather, you're better off getting something from leatherique instead.
Looks good, doesn't it.