When choosing antifreeze don't be mislead by the color! In fact, unless you open the bottle and pour some out you won't know what color you are getting in the first place. What to look for is the information on the label.
Typically the "Red" antifreeze is extended life 150,000 mile (5Yr) antifreeze, infamously made familiar by GM's trademark Dex-Cool. While the "Green" solution has been the good ole 12-24 month service life stand bye for many year. In fact you can also find the colors of Blue, Orange, and Yellow. The colors are additives, meant to distinguish one set of properties from another. Unfortunately the colors, and additives do not neccisarily match from supplier to supplier. Be sure to read the labels, and heed the advice below.
So whats the best advice?
Firstly, read your vehicles owner's manual and identify the recommended call out for the engine coolant. Read the labels carefully to be certain the bottle in your hand is matched with that recommended in your vehicle manual.
If in doubt, drain it out! If you can not determine what your current antifreeze is, drain the entire system, flush it clean, and refill according to manufactures recommended mix ratio. Never Never mix different antifreeze types. The combinations of chemicals can cause unwanted oxidation ,corrosion, and degradation of cooling properties.
Keep levels proper. Low levels can allow excess air, coolant cavitation, and yes accelerated corrosion to your cooling system.
Never mix with tap water! Tap water has chemicals that can combine with those in the antifreeze, and cause effects.
Check your coolant specific gravity with a hydrometer. This simple device only cost a few dollars at most autoparts stores. It will tell you when your coolant needs to be changed. Check your level monthly, and the specific gravity seasonally.