I was wondering if someone could explain to me the difference between full mercury fluorescent tubes and modern fluorescents that use way less mercury? I have an old Philips 8W halophosphate 640 tube and it seems the halo contains more of a blue/green tinge around the edges. It would seem this is a result of more mercury vapour in the tube. I could also just be seeing this wrong.

Is there any advantage over the modern tubes? Are they more collectable?

The EU has banned halophosphate tubes a long time ago but I want to start collecting them. What would be the golden age for fluorescent tubes in the EU? Thanks

The total mercury dose does not have any influence, assuming the tube is good. Regardless of the dosage method, the operating pressure of the Hg vapor should end up the same, so the same glow colors. The modern tubes just tend to utilize more of the mercury dose into the gas mixture.
However this may not be fully true when the lamp is still warming up. Old tubes with liquid mercury in them have the operating pressure immediately on start. But some of the modern amalgam designs tend to absorb quite a big part back into the pellet when the lamp is off, so after start it has to evaporate and distribute along the tube back.

But there were other, way more dominant changes in fluorescent chemistries, which do have direct effect on the end glow:
The buffer gas. Old lamp designs, like 20..65W T12, but as well the miniature 4..13W T5 lamps used just argon as a buffer gas.
Then the T8 retrofit came (18, 36, 54W,...), which use Krypton as the main buffer component (in a mixture along with Argon).
Then came the modern T5HE and T5HO and many CFLs, which use still different mixtures. Each family has different gasses, but as well the different designed operating mercury pressure, so each will behave in a different way regarding the end glows or so.

And of course changes in electrode assembly design may influence the end glow as well (what material gets sputtered and how much,...)