Use multi uv-maps and mask texture to make material, which allows to change numbers for every single object.
00:00 overview
01:15 set up workspace
01:41 base texture
02:24 mask for circle under numbers
04:29 uv-map and mask for left number
07:08 uv-map and mask for right number
08:12 switching numbers
10:48 combine masks
11:38 custom color for circle