I dug out 'The New Breed' and a book on British equipment.
The arm of service marking (the square with the number in it) should be red (senior brigade) or green (junior brigade). The red and blue unit sign is Royal Artillery and should be dropped. Green over blue was reconnaissance - I don't think recon units used Shermans, so these are unnecessary.
For armoured divisions the numbers should be:
50 (Brigade HQ), 51, 52, 53 (regiments). So these are correct.
8th Army and other middle east units used a different sequence, which carried on into the Italian campaign.
71 (Brigade HQ), 40, 86, 67 (regiments). So these should all be available at least in red.
The other numbers can be dropped.