“Red as ruby” would convey a single color resemblance. The image of red banners on green shafts adds the flower’s petals and stem as an arranged visual whole.
Subject: a single shaqīq flower.
Model: red banners displayed on green spears.
Ground: a spread of red above or around a slender green support.
Several physical details may be understood in a single subject while the explicit comparative model is a composite image.