Gladiolus flowers of several species have colour variations that make identification difficult and sometimes impossible, especially when you only have a picture and no further access to the specimen photographed. This flower found north of Melkbosstrand clearly required some better scrutiny as the photo isn’t going to yield a definitive answer unless one knows the plant very well.
The guess is Gladiolus carinatus
or blue Afrikaner, but Gladiolus gracilis
keeps coming into the reckoning as well. The markings on the lower tepals should be a clue, but are not depicted clearly. The sharp indent at the tips of the tepals should also help. But help is still surely needed and you are welcome to add a comment!