Phthalo Green is an almost fluorescent green color. Because of its transparent quality, it can be used atop Black Gesso to create gorgeous effects, including those found in Bob's "northern lights" paintings. One of fourteen warm clean colors, yielding endless numbers of natural combinations in a smooth yet firm consistency necessary to the Bob Ross Wet-on-Wet Technique. No other paints can accomplish what these do, and every batch is individually tested for perfection.