The colour of Antifreeze is not important as you can have the same antifreeze but be two different colours. Thus, in theory the colour is not relevant. However, we would never recommend mixing two different Antifreezes together. What would likely happen is a chemical reaction between the antifreezes which would nullify the quality of them. This would then potentially damage your Alde system. Alde G12++ or Alde G13 can be added to any system and will not react with the antifreeze currently in your system.