We report an experimental study on shape deformations of ternary vesicles undergoing phase separation under an osmotic pressure difference. The phase separation on various shape vesicles causes unique shape-deformation branches. In the domain coarsening stage, prolate, discocyte, and starfish vesicles show a shape convergence to discocytes, whereas a pearling instability is observed in tube vesicles. In late stages, the domains start to bud towards the inside or outside of the vesicle depending on the excess area. We discuss the deformation branches based on the membrane elasticity model.