Anything you put in it will be better than it has now, don't go near Halfords unless you have a trade card, find a proper motor factors instead, should work out alot cheaper.
The Comma XStream G48 is actually green in colour, the same as normal blue stuff as far as I know though.
Blue is recommended but red is just as compatible imo, if it wasn't I would have two Pandas with no coolant and a big puddle on the floor. Anything you put in it will be better than it has now.
Have you checked to see what colour is actually is at the moment?
Will report back on colour later, think it's blue though