Mica powder pigments can safely be added to TotalBoat Halcyon varnish at low percentages to create a wide variety of colors, but it's not recommended to add other dyes, pigments, or tints to TotalBoat Halcyon, due to potential incompatibility concerns that may compromise the coating's performance.
If it is still desired to attempt tinting Halcyon with other materials, only use water-based tints, or tints that are compatible with water-based materials, and always perform a small test sample before ever attempting to use tinted Halcyon on the final project, to ensure that the Halcyon cures properly, adheres to the substrate as desired, and develops the desired hardness. Typical safe amounts of pigments or tints will range from .5-2%.