Good question! We believe that this should be OK on most occasions, but we can’t guarantee that the resin will act as promised if you mix the colours. It is important to understand that different colours require varying amounts of photo-initiator, so when mixing some colours there may be problems with curing and the durability of the resin once it is cured. We would suggest you only mix enough to make a small ‘test’ model to ensure it will work as expected. We will not refund resins that have been mixed, so this will be done at your own risk! Alternatively, you can purchase our CMYK pigment set to create custom resin colours.