There were a couple of BRG's used by BMC over the years. You can find the old paint codes here -
viewtopic.php?f=25&t=66469But those old codes won't be much use to you if you are matching against a painted car as the colour will have changed somewhat over the years. In any case the old tinters aren't available. I suggest you get your current car colour matched by eye or machine. There are many automotive paint suppliers that will do this. Take along the rear number plate flap and they will mix a matching colour.
