For my 1.6 TU Petrol engine I personally use red antifreeze, primarily "Ready Mixed 50/50 Triple QX Red" frankly because I can source it easily and it's cheap.
I did some reading into the difference between each coolant and for my 2001 Phase 3 it suggested: Ethylene glycol based Antifreeze (Red), incorporating Organic Acid Technology (OAT). Upto -36 C upon dilution.
See if you can shine a light down your radiator cap, I'm guessing it's probably going to be pretty murky though. Red antifreeze looks a lot like rusty water when you can't see much. Lol. If you can, try obtaining a sample of the coolant before topping it up. It's important to establish what's best for YOUR car first, what's good for my 1.6 might be slightly different for your 1.4. Always best to research.
If you wanted to completely change the coolant you could throw in some water to top it off to obtain a sample (you'd be flushing it later anyway). However if you are literally just topping up with antifreeze, it would make deciding on what color slightly more difficult. Ideally you wont want to mix antifreeze colors.
Edit:
If you do shine a light down the radiator cap, you might be able to use the ridges on the inside as a rough gauge. Hope this helps.
I did some reading into the difference between each coolant and for my 2001 Phase 3 it suggested: Ethylene glycol based Antifreeze (Red), incorporating Organic Acid Technology (OAT). Upto -36 C upon dilution.
See if you can shine a light down your radiator cap, I'm guessing it's probably going to be pretty murky though. Red antifreeze looks a lot like rusty water when you can't see much. Lol. If you can, try obtaining a sample of the coolant before topping it up. It's important to establish what's best for YOUR car first, what's good for my 1.6 might be slightly different for your 1.4. Always best to research.
If you wanted to completely change the coolant you could throw in some water to top it off to obtain a sample (you'd be flushing it later anyway). However if you are literally just topping up with antifreeze, it would make deciding on what color slightly more difficult. Ideally you wont want to mix antifreeze colors.
Edit:
If you do shine a light down the radiator cap, you might be able to use the ridges on the inside as a rough gauge. Hope this helps.