I'd check the Caltex coolant before changing. Is it an OAT (organic Acid Technology) or ethylene glycol based coolant ? Coolant colour doesn't mean much now either. Green was good for older vehicles (ethylene glycol) but manufacturers dye OAT coolant any colour they like.
OAT isn't always suitable for older vehicles.
Have a read of this article.....
Warning about engine coolant!!!!! - TR Register Forum
Search the net and it becomes very confusing. Ethylene glycol, propylene glycol, OAT (organic acid technology and IAT (inorganic acid technology) coolants are available. Modern vehicles are designed to use OAT or IAT but with an older vehicle you need to be very careful that it provides corrosion protection without damaging gaskets etc.