Firstly the 2nd New Zealand Division was not normal
Prior to it's first action in 1940 there had been a desire to have an armoured unit within the NZ Division, but approval from GHQ was not forth coming and they were organized as a standard infantry division. During the defence of Alamein the 4th Infantry Brigade suffered heavy losses, in part due to a lack of armour support. This gave further impetus for NZ General Staff to push for an integral Armoured Unit. In September 1942 GHQ MEF gave it's approval and within a month the 4th NZ Infantry Brigade became the 4th NZ Armoured Brigade and it's three infantry regiments (18,19 & 20) became Armoured Regiments. With this change the 2nd NZ Div went from being a standard infantry division to a composite or mixed division, comprising an Armoured Brigade and two Infantry Brigades along with all the other supporting units.
Since the organisation of the 2nd NZ Div did not fit the standard pattern for AoS numbering, I can only assume that a new series was drawn up for them GHQ MEF. 4th Armd Bde's numbers were as follows:
HQ 4 NZ Armd Bde 65
18th Armd Regt 91
19th Armd Regt 80
20th Armd Regt 52
All numbers were in white on a RED background (that is the official line). As for why they are on black in the Crusader, I would take it that was the only paint available at the time. As for the placement of the formation sign above the AoS number, this seems to have been common practice within the 2nd NZ Div.