The general purpose pigments, like Fiberlay's, are solvent-based. the percentage recommended for epoxy is the most you can use without seriously degrading the epoxy. Another problem is that the thicker the coat, the harder it is for the solvents to evaporate. At some thickness, no matter how little you use, it doesn't evaporate because it is trapped.

System 3 (Maybe Raka from the postings) is pigmented resin. You can use as much as you want. Just make sure you consider the amount of pigmented resin when you add hardener.

You might talk to your epoxy manufacturer and find out if there are any powder pigments that are acceptable.