British WWII AFV markings are a bit of a varied subject area. The system was kind of complicated and some things changed/evolved during the war. A basic rule of thumb is that there will be a unit insignia (brigade/division/corps/army) flash on one side, and an Arm of Service flash (colored square, usually with a number) to denote the type of unit- tank, infantry, recon, signals, etc. on the opposite corner. Then the sub unit will be a geometric shape with or without a number inside to denote that element. Colors of the shape varied by "seniority" of the battalion/regiment. Confused yet?
If you decide on a particular unit and time period, such as the unit you listed, you can figure out the markngs you want.
F is for FIRE, That burns down the whole town!
U is for URANIUM... BOMBS!
N is for NO SURVIVORS...
- Plankton
LSM