: 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.

System 3's website says:

"You may add these pigments to our basic epoxy resins or the WR-155 Activator to produce a pastel-tinted water-reducible primer. One jar of pigment will tint a gallon of finished product." (http://www.systemthree.com/pdf/sys3_web_catalog_01.pdf)

They sell these pigments in 4-oz. jars, so the maximum recommended concentration is 4 oz./gal, or 4 oz./128 oz., or just over 3%. While it may work to load up the resin at higher concentrations, that is not what the manufacturer recommends. While the S3 literature does not say so, the most common result from high colorant loading is to plasticize the epoxy end product, reducing its strength, and promoting joint creep and printthrough of the fabric. Furthermore, they say the result is a pastel-tinted product, not an opaque one.

Fiberglass boat hulls are universally white. Dings in glass surfaces produce white scars. The white in the gelcoat and wetout resin tends to mask those dings. Those scars are caused by fracturing of the glass itself, and even a tinted layup resin won't prevent the white scars. So the bottom line is, unless it's tinted white, it won't really do the job. It's just added time, expense and complexity. That's the best case. Worst case is that the strength of the composite is compromised. Cost/benefit analysis says tinting fill coats is a loser.