Phtahlos are dyes. Phthalocyanine pigments have fine particle sizes so they have a high staining quality. This can make them difficult to control, but they are not dyes. Try using Phthalo Green Yellow Shade , which is much warmer, and therefore relates to the world and psyche better than Phthalo Green . Flake white is better because it does not crack.
All white pigments have positive and negative characteristics.
Flake White can crack in large cracks. Zinc becomes brittle. Titanium looks chalky. By combining titanium with zinc the paint tends to exhibit a balance between strength and flexibility and to be less prone to the negative characteristics of the pigments used solo. Since its ok to use acrylic gesso its ok to under paint oils with acrylic paints.