A distinct cultivar of Argyranthemum plant named `Supamarg`, characterized by its compact, uniform, upright to outwardly spreading, and mounded plant habit; freely branching habit, dense and bushy plants; glossy dark green foliage; freely flowering habit with numerous inflorescences per plant; single inflorescence form; pink and white bi-colored ray florets and disc florets that are initially dark red at the apex and become bright yellow with development.