Pearl is strange. One copy of the gene alone will not change the color of a black, bay, or chestnut horse. However, two copies will produce colors similar to a single cream dilute or a champagne color (kind of the same way cream does not change black, but two cream genes will change it entirely). Furthermore, pearl will suddenly become evident if a horse carries pearl and cream and be double diluted. For instance, a buckskin pearl will appear to be an almost perlino color.
ETA: Wyndella, by "blue/green eyes", they mean just that: eyes that are a bluish-green color. Not one green, one blue.