You will find it on the datacard (Datenkarte). In case you do not have it, you can order it from an MB dealer for about EUR 150 and upon presenting proof of ownership.
You can also check briefly recommended color combinations upholstery/paint in our Technical Manual - but this may not give you a definite answer to your question - it only shows MB recommended color combinations, if a customer wanted to order a different one, it might have been followed by a substantial prepayment, so not very often exercised. If you spot your paint color and you will see that there is no e.g. red upholstery recommended for it, chances are it is not red that you originally had. But it is not a precise indication.