In this comprehensive article, the author discusses the value factors of colored gems in five parts. Parts one and two appeared in Gem Market News, January/February 2016, Volume 35, Issue 1. What follows are parts three and four. Part 3: Darkness and Brightness Part 1 discussed the major value factors that affect the price of a colored gemstone, and broke down the various aspects of cut quality (one of the factors of value). Part 2 defined aspects of cutting styles to establish some common language, with a focus on basic faceting styles, and a short discussion on cabochons and beads. Since the color quality is such an important part of the value, parts 3 and 4 will focus on factors that affect value related to color, and examine how a cutter makes choices when cutting a gem. Wireframes or depictions of facet arrangements (such as the left side of Fig. 3-09) are from scans of real gems so as to illustrate aspects of gem cutting. Face-up patterns (such as the right side of Fig. 3-09) were made using the program DiamCalc; adjustments were made to the refractive index to represent the gem material being demonstrated. DiamCalc does not show double refraction. [caption id="attachment_6869" align="aligncenter" width="300"] Fig. 3-11. Citrine top and side view. Pre-formed by Werner Anschvetz, cut and polished by Hans J. Roehrig. Photo by Orasa Weldon, © GIA.[/caption] Tradeoffs Before discussing how the trade assesses relative value of colored gems, it is important to realize that you will often see examples where the cutter had to....