A new and distinct cultivar of Hydrangea plant named ‘；Hokomagrejo’；, characterized by its upright to somewhat outwardly spreading plant habit； vigorous growth habit and moderate to rapid growth rate； freely branching habit with strong and thick sturdy stems； freely flowering habit； large mophead-type inflorescences with yellow green-colored sterile flowers with red purple-colored centers and margins； and good postproduction longevity.
