So it seems the lower the wattage the lower the colour temperature, is there any explanation for this? there is a very clear difference in color temperature between my 70w and 1000W HPS lights, and even between my 100W and 70W HPS there seems to be a slight difference... I have all three going right now and I'm noticing  it, I wish I had my 400 and 150 watters going so i could run them all side by side... unfortunately That'd probably be pushing the upper limits of my electrical supply,...

I've don't seen difference between the color of low wattage HPS like 70W and higher wattage like 150W, 250W and 400W. The color differences is really visible when the lamp is redding out near EOL (The color than differs between individual lamps) or if it is a mercury free HPS lamp (Than it is much golden yellow than a regular HPS lamp).

I do have the same impression (over here - 230V), but thinking of it i seen many lamps burning at slightly different temps, so can't say this is a rule

Generally, i seen more 70W and few 100W lamps looking underpowered, 150W (S56) mostly normal, and more 250W+ lamps overpowered

Few factors that may explain this :

 - Most 70W lamps are 70W SON E/I. They are started with an internal glow starter, that pretty much limits the available voltage to 1kV at best, while the "Super" lamps won't even show a flash with 1kV. The lamps could very possibly have really lower pressure than the "Super" lamps

 - Most low power lamps are used in footpaths, that could be supplied with quite long underground cables, contributing to voltage drop

 - Over here, big transformers (typically 400kVA) supply entire blocks of houses. In a small village, a handful of those transformers could be supplying the entire place. Their voltage might be a bit lowered by general load in the area (this is accounted for - The power company aims to supply 240V, so in reality they end up around 230V after the voltage drops). In contrast, transformers supplying lighting on some intercity road are often the same 400kVA size but supply only the lighting installation, they could be running nearly unloaded. The lighitng installation could be getting 240V+, maybe even 250V in some places

 - Maybe some common ballast model is out of spec as a rule ?

Also, there seems to be some regional relation : There are places where HPS lamps look overpowered as a rule, of many different wattages in different luminaires. In Jerusalem for example (lanterns are mostly Thorn Pilote T2 and Schreder Z2 & Z3), all of them look like they are getting atleast some 250..260V instead of the 230. I dont have an explanation but this really stands out