Been looking around at decals mate - Hannant's have a sheet of 'standard' Luftwaffe numbers, but not the late war style and colours. Seems only Peddinghaus have them and then in limited styles/colours.
I've created some numbers and letters by reverse masking, but these have all been 'angular' - 4,7,E.H etc. I did once try using decals over the colour to reverse mask, but it wasn't very successful (need to do similar for a He111 and Bf110, so still thinking about it.)
I can probably make coloured number decals close to the shade needed, but density isn't very good on clear decal sheet, and of course white is a 'no go'. It can sometimes work to lay two decals, one on top of the other, or make the decal and then paint over that, but both methods are very hit an miss.