Gordon, Robert Mellichamp's book was the first source I tried for info, but he only gives drawings for 2 types of Practice projectile, and the nose-fuzed common shell. Although there is a passing reference to a day-tracer in the details of the colour codes for the 1.5-pdr Vickers, and also in the section on the 1-Pdr round (where he says he thinks the 1.5-Pdr projectiles were designed along similar lines), there seems to be no further information there.
The other study that you mentioned, if it is the one you kindly supplied to me a couple of years ago, relates solely to the C.O.W. gun rounds, rather than those for the Vickers gun, which as you know use totally different cases and projectiles.
Glevum, your very nice round that you show is also for the COW gun, and as such would have had a chemical tracer (i.e., an igniferous one) rather than the liquid one that the 1-Pdr had.
Perhaps The Otter can help??
Regards,
Roger.