I would highly advise that you DO NOT mix different coolants. If the types of coolant are the same, then you can safely mix them (and I don't mean just checking to see if the colors are similar).
However -- If you are going to do a thorough distilled water flush and coolant replacement, then you can change to a different type of coolant (make sure it agrees with what your owner manual says). I flush with 3 gallons of distilled water...until it drains out clear...or close to it.
Personally I use the manufacturer recommended coolant only. Pentofrost is the same part-number as Hyundai Long Life coolant the last I checked. It is NOT pre-diluted, so you'll want to have a decent sized measuring container (1 gal enough). Also, not all of the water will drain from the system if you flush the system, so account for the extra water in the system when you determine your mix ratio.