Painting
(a) High explosive shell are painted yellow.
(b) Shrapnel shell are painted black.
(c) Smoke bursting shell are painted green.
(d) Armour-piercing shell filled H.E. are painted yellow to the shoulder, with the head green.
(e) High explosive shell for use with reduced charges have the body from driving band to green band painted white, remainder yellow.
Stencilling
1. Tips of shell
(a) Red tip denotes shrapnel.
(b) Black tip denotes absence of smoke box in amatol filled shell.
2. Rings round the head
(a) Red ring indicates that shell is filled.
(b) A ring of red crosses in place of the red ring denotes amatol or T.N.T. filled shell suitable for hot climates.
(c) A black ring above the red ring indicates that the shell is fitted with exploders, only suitable for a powder-filled fuze.
(d) Two white rings, one above and one below the red ring, denote armour-piercing.
(e) A light brown ring above the red ring on smoke bursting shell denotes shell is of cast iron or semi-steel.
3. Bands round the body
(a) Green band round centre denotes shell filled with amatol or T.N.T.
(b) Two black bands denotes H.E. practice projectile.
(c) One black band round body denotes empty H.E. shell to be used for drill purposes.
I'd guess that the orange band is just a faded red band.
Source: Handbook for the Ordnance, Q.F. 18-PR Marks I, I*, II and II*. 1940