Not British, but I am Canadian, eh. Being of the Commonwealth though is still difficult to give a complete answer. For your question, it would be a qualified yes.
During the African campaign British armour divisions went through a number of organizational changes. According to Osprey's publication Desert Rats British 8th Army in North Africa 1941-43: the period from February to August 1942 had anti-tank units grouped into the artillery regiment of an armoured division.
Before this date, AT units were a regiment unto themselves and was up to the commander of the (armour) Div. as to how he wanted to deploy them within the division. In August, after the battle of Gazala, AT units were again found as an individual regiment within the armoured division. They were also found at company strength within a motorized infantry brigade (attached to the armoured brigade) as well as another three companies with the motorized infantry brigade (AT comapany with each of the three infantry battallions).
I haven't found any desert pics or a chart presentation for the number you are looking for. A background colour of red top/blue bottom is definitely artillery, but have no official date when this was started. The tactical number 46 seems to crop up now and then on web searches.
Above picic is from a UK forum, where an individual was looking for an explanation of the number sign.
Following was a response:
Red & Blue horizontal is RA.
46 is the serial no for RA Light Regiment (as opposed to Field Regt which used 42, 43, 44).
47 is the callsign for FAC
regards.
Jack