A point-of-sale custom color system for tinting base paints and stains includes an array of water-only fluid colorants, including at least white, green, blue and red water-only colorants, which can be used to tint water-borne paints and stains. When tinting solvent-borne base paints or stains, a synergist containing one or more surfactants and optional dispersing agents or optional cosolvents is added to or is a part of the solvent-borne base paint or stains, and enables effective tinting using the water-only colorants.