Usually the rule is to stick with the colour that's in there. I use the green stuff in my 87 and 79 (which has a 74-76 engine in it). The manufacturer is Comma. Don't seem to have any issues with it, been running it for 2 years daily use and it's clean as a whistle in my 87. The difference in coolants is the types of metals they're suited to and not suited to. Ours are iron and copper (radiator). Newer cars have a lot of aluminium and use the pink coloured fluid. There are whole threads of info out there, so that's just a very brief summary, sorry.
I buy the concentrate as i'm not a fan of paying for water
I got one 5 litre concentrate bottle and used it for a coolant flush, then used that empty bottle as a 50/50 mix bottle... it's got markings on the side so filled it to the 2 litre mark with distilled water, then bought a 5 litre concentrate and poured it into the bottle with water in it, up to 4 litres, so now when i need to top up, i know it's exactly 50/50 going in. My manual has gone for a walk so i can't check but it says in there that the requirement is glys...something. Glycol? Glyserin? Both used in foods and antifreeze, yummy.