Aqua is a cream, water-based formulation; Velvet is a glycerine base formulation. Because of this Velvet will be thicker. However, since both are manufactured at our facilities, there is no problem with mixing the 2 different formulations together. However, keep in mind to mix thoroughly in order to keep the mixtures of the glycerine base and water base together. DO NOT mix from different company pigments together. We don't recommend or advise to mix pigments made from a different manufacturer.